diff --git a/icu4c/as_is/os400/unpax-icu.sh b/icu4c/as_is/os400/unpax-icu.sh
index a6fc31174eb..869e855c349 100755
--- a/icu4c/as_is/os400/unpax-icu.sh
+++ b/icu4c/as_is/os400/unpax-icu.sh
@@ -25,6 +25,9 @@ else
 fi
 export QSH
 
+# set this to "v" to list files as they are unpacked (default)
+VERBOSE_UNPACK="v"
+
 # Set the following variable to the list of binary file suffixes (extensions)
 
 
@@ -78,13 +81,13 @@ echo "Extracting from $tar_file ..."
 echo ""
 
 # extract everything as iso-8859-1 except these directories
-pax -C 819 -rcvf $tar_file $ebcdic_data
+pax -C 819 -rc${VERBOSE_UNPACK}f $tar_file $ebcdic_data
 
 # extract files while converting them to EBCDIC
 echo ""
 echo "Extracting files which must be in ibm-37 ..."
 echo ""
-pax -C 37 -rvf $tar_file $ebcdic_data
+pax -C 37 -r${VERBOSE_UNPACK}f $tar_file $ebcdic_data
 
 #****************************************************************************
 # For files we have restored as CCSID 37, check the BOM to see if they    
@@ -139,7 +142,9 @@ fi
 
 echo "# Processing special paths."
 # Process special paths
-more_bin_files=$(find icu -type f \( -name '*.zzz' `echo $binary_suffixes | sed -e 's%[a-zA-Z]*%-o -name \*.&%g'` \)  -print)
+more_bin_opts=$(echo $binary_suffixes | sed -e 's%[a-zA-Z0-9]*%-o -name \*.&%g')
+# echo "Looking for additional files: find ... $more_bin_opts"
+more_bin_files=$(find icu -type f \( -name '*.zzz' $more_bin_opts \)  -print)
 echo "Restoring binary files by special paths ($bin_count) ..."
 rm $more_bin_files
 pax -C 819 -rvf $tar_file $more_bin_files
diff --git a/icu4c/source/test/intltest/alphaindextst.cpp b/icu4c/source/test/intltest/alphaindextst.cpp
index 1df7d29d00b..763889c4c96 100644
--- a/icu4c/source/test/intltest/alphaindextst.cpp
+++ b/icu4c/source/test/intltest/alphaindextst.cpp
@@ -569,7 +569,7 @@ void AlphabeticIndexTest::TestHaniFirst() {
     bucketIndex = index.getBucketIndex(UnicodeString((UChar)0x03B1), status);
     assertEquals("getBucketIndex(Greek alpha)", 27, bucketIndex);
     // U+50005 is an unassigned code point which sorts at the end, independent of the Hani group.
-    bucketIndex = index.getBucketIndex(UnicodeString(0x50005), status);
+    bucketIndex = index.getBucketIndex(UnicodeString((UChar32)0x50005), status);
     assertEquals("getBucketIndex(U+50005)", 27, bucketIndex);
     bucketIndex = index.getBucketIndex(UnicodeString((UChar)0xFFFF), status);
     assertEquals("getBucketIndex(U+FFFF)", 27, bucketIndex);
@@ -598,7 +598,7 @@ void AlphabeticIndexTest::TestPinyinFirst() {
     bucketIndex = index.getBucketIndex(UnicodeString((UChar)0x03B1), status);
     assertEquals("getBucketIndex(Greek alpha)", (int32_t)27, bucketIndex);
     // U+50005 is an unassigned code point which sorts at the end, independent of the Hani group.
-    bucketIndex = index.getBucketIndex(UnicodeString(0x50005), status);
+    bucketIndex = index.getBucketIndex(UnicodeString((UChar32)0x50005), status);
     assertEquals("getBucketIndex(U+50005)", 27, bucketIndex);
     bucketIndex = index.getBucketIndex(UnicodeString((UChar)0xFFFF), status);
     assertEquals("getBucketIndex(U+FFFF)", 27, bucketIndex);
diff --git a/icu4c/source/test/intltest/datadrivennumberformattestsuite.cpp b/icu4c/source/test/intltest/datadrivennumberformattestsuite.cpp
index 88765d72edb..254404e456d 100644
--- a/icu4c/source/test/intltest/datadrivennumberformattestsuite.cpp
+++ b/icu4c/source/test/intltest/datadrivennumberformattestsuite.cpp
@@ -110,7 +110,7 @@ DataDrivenNumberFormatTestSuite::~DataDrivenNumberFormatTestSuite() {
 }
 
 UBool DataDrivenNumberFormatTestSuite::breaksC() {
-    return (NFTT_GET_FIELD(fTuple, breaks, "").toUpper().indexOf(0x43) != -1);
+    return (NFTT_GET_FIELD(fTuple, breaks, "").toUpper().indexOf((UChar)0x43) != -1);
 }
 
 void DataDrivenNumberFormatTestSuite::setTupleField(UErrorCode &status) {
diff --git a/icu4c/source/test/intltest/itrbnf.cpp b/icu4c/source/test/intltest/itrbnf.cpp
index ddd6aea9e96..d9d7489241f 100644
--- a/icu4c/source/test/intltest/itrbnf.cpp
+++ b/icu4c/source/test/intltest/itrbnf.cpp
@@ -2124,7 +2124,7 @@ void IntlTestRBNF::TestPluralRules() {
 
     // Make sure there are no divide by 0 errors.
     UnicodeString result;
-    RuleBasedNumberFormat(ruRules, Locale("ru"), parseError, status).format(21000, result);
+    RuleBasedNumberFormat(ruRules, Locale("ru"), parseError, status).format((int32_t)21000, result);
     if (result.compare(UNICODE_STRING_SIMPLE("twenty-one thousand")) != 0) {
         errln("Got " + result + " for 21000");
     }
diff --git a/icu4c/source/test/intltest/measfmttest.cpp b/icu4c/source/test/intltest/measfmttest.cpp
index 9830ecc5421..08ad11c7d32 100644
--- a/icu4c/source/test/intltest/measfmttest.cpp
+++ b/icu4c/source/test/intltest/measfmttest.cpp
@@ -999,17 +999,17 @@ void MeasureFormatTest::TestExamplesInDocs() {
     if (!assertSuccess("Error creating formatters", status)) {
         return;
     }
-    Measure measureC(23, MeasureUnit::createCelsius(status), status);
-    Measure measureF(70, MeasureUnit::createFahrenheit(status), status);
+    Measure measureC((double)23, MeasureUnit::createCelsius(status), status);
+    Measure measureF((double)70, MeasureUnit::createFahrenheit(status), status);
     Measure feetAndInches[] = {
-            Measure(70, MeasureUnit::createFoot(status), status),
-            Measure(5.3, MeasureUnit::createInch(status), status)};
+            Measure((double)70, MeasureUnit::createFoot(status), status),
+            Measure((double)5.3, MeasureUnit::createInch(status), status)};
     Measure footAndInch[] = {
-            Measure(1, MeasureUnit::createFoot(status), status),
-            Measure(1, MeasureUnit::createInch(status), status)};
+            Measure((double)1, MeasureUnit::createFoot(status), status),
+            Measure((double)1, MeasureUnit::createInch(status), status)};
     Measure inchAndFeet[] = {
-            Measure(1, MeasureUnit::createInch(status), status),
-            Measure(2, MeasureUnit::createFoot(status), status)};
+            Measure((double)1, MeasureUnit::createInch(status), status),
+            Measure((double)2, MeasureUnit::createFoot(status), status)};
     if (!assertSuccess("Error creating measurements.", status)) {
         return;
     }
@@ -1067,28 +1067,28 @@ void MeasureFormatTest::TestExamplesInDocs() {
 
 void MeasureFormatTest::TestFormatPeriodEn() {
     UErrorCode status = U_ZERO_ERROR;
-    Measure t_19m[] = {Measure(19, MeasureUnit::createMinute(status), status)};
+    Measure t_19m[] = {Measure((double)19, MeasureUnit::createMinute(status), status)};
     Measure t_1h_23_5s[] = {
-            Measure(1.0, MeasureUnit::createHour(status), status),
-            Measure(23.5, MeasureUnit::createSecond(status), status)
+            Measure((double)1.0, MeasureUnit::createHour(status), status),
+            Measure((double)23.5, MeasureUnit::createSecond(status), status)
     };
     Measure t_1h_23_5m[] = {
-            Measure(1.0, MeasureUnit::createHour(status), status),
-            Measure(23.5, MeasureUnit::createMinute(status), status)
+            Measure((double)1.0, MeasureUnit::createHour(status), status),
+            Measure((double)23.5, MeasureUnit::createMinute(status), status)
     };
     Measure t_1h_0m_23s[] = {
             Measure(
-                    1.0,
+                    (double)1.0,
                     TimeUnit::createInstance(
                             TimeUnit::UTIMEUNIT_HOUR, status),
                     status),
             Measure(
-                    0.0,
+                    (double)0.0,
                     TimeUnit::createInstance(
                             TimeUnit::UTIMEUNIT_MINUTE, status),
                      status),
             Measure(
-                    23,
+                    (double)23.0,
                     TimeUnit::createInstance(
                             TimeUnit::UTIMEUNIT_SECOND, status),
                     status)
@@ -1617,8 +1617,8 @@ void MeasureFormatTest::helperTestMultiples(
         return;
     }
     Measure measures[] = {
-            Measure(2, MeasureUnit::createMile(status), status),
-            Measure(1, MeasureUnit::createFoot(status), status),
+            Measure(2.0, MeasureUnit::createMile(status), status),
+            Measure(1.0, MeasureUnit::createFoot(status), status),
             Measure(2.3, MeasureUnit::createInch(status), status)};
     if (!assertSuccess("Error creating measures", status)) {
         return;
@@ -1634,8 +1634,8 @@ void MeasureFormatTest::helperTestMultiples(
 void MeasureFormatTest::TestManyLocaleDurations() {
     UErrorCode status = U_ZERO_ERROR;
     Measure measures[] = {
-            Measure(5, MeasureUnit::createHour(status), status),
-            Measure(37, MeasureUnit::createMinute(status), status)};
+            Measure(5.0, MeasureUnit::createHour(status), status),
+            Measure(37.0, MeasureUnit::createMinute(status), status)};
     if (!assertSuccess("Error creating measures", status)) {
         return;
     }
@@ -1697,8 +1697,8 @@ void MeasureFormatTest::TestGram() {
     if (!assertSuccess("Error creating format object", status)) {
         return;
     }
-    Measure gram(1, MeasureUnit::createGram(status), status);
-    Measure gforce(1, MeasureUnit::createGForce(status), status);
+    Measure gram((double)1, MeasureUnit::createGram(status), status);
+    Measure gforce((double)1, MeasureUnit::createGForce(status), status);
     if (!assertSuccess("Error creating measures", status)) {
         return;
     }
@@ -1821,7 +1821,7 @@ void MeasureFormatTest::TestFieldPosition() {
             NumberFormat::kDecimalSeparatorField,
             10,
             11);
-    measure = Measure(43, MeasureUnit::createFoot(status), status);
+    measure = Measure(43.0, MeasureUnit::createFoot(status), status);
     if (!assertSuccess("Error creating measure object 2", status)) {
         return;
     }
@@ -1843,16 +1843,16 @@ void MeasureFormatTest::TestFieldPositionMultiple() {
         return;
     }
     Measure first[] = {
-            Measure(354, MeasureUnit::createMeter(status), status),
-            Measure(23, MeasureUnit::createCentimeter(status), status)};
+      Measure((double)354, MeasureUnit::createMeter(status), status),
+      Measure((double)23, MeasureUnit::createCentimeter(status), status)};
     Measure second[] = {
-            Measure(354, MeasureUnit::createMeter(status), status),
-            Measure(23, MeasureUnit::createCentimeter(status), status),
-            Measure(5.4, MeasureUnit::createMillimeter(status), status)};
+      Measure((double)354, MeasureUnit::createMeter(status), status),
+      Measure((double)23, MeasureUnit::createCentimeter(status), status),
+      Measure((double)5.4, MeasureUnit::createMillimeter(status), status)};
     Measure third[] = {
-            Measure(3, MeasureUnit::createMeter(status), status),
-            Measure(23, MeasureUnit::createCentimeter(status), status),
-            Measure(5, MeasureUnit::createMillimeter(status), status)};
+      Measure((double)3, MeasureUnit::createMeter(status), status),
+      Measure((double)23, MeasureUnit::createCentimeter(status), status),
+      Measure((double)5, MeasureUnit::createMillimeter(status), status)};
     if (!assertSuccess("Error creating measure objects", status)) {
         return;
     }
@@ -1937,9 +1937,9 @@ void MeasureFormatTest::TestGroupingSeparator() {
     Measure ms[] = {
             Measure((int32_t)INT32_MAX, MeasureUnit::createYear(status), status),
             Measure((int32_t)INT32_MIN, MeasureUnit::createMonth(status), status),
-            Measure(-987, MeasureUnit::createDay(status), status),
-            Measure(1362, MeasureUnit::createHour(status), status),
-            Measure(987, MeasureUnit::createMinute(status), status)};
+            Measure(-987.0, MeasureUnit::createDay(status), status),
+            Measure(1362.0, MeasureUnit::createHour(status), status),
+            Measure(987.0, MeasureUnit::createMinute(status), status)};
     FieldPosition pos(NumberFormat::kGroupingSeparatorField);
     UnicodeString appendTo;
     fmt.formatMeasures(ms, 5, appendTo, pos, status);
@@ -1958,8 +1958,8 @@ void MeasureFormatTest::TestDoubleZero() {
     UErrorCode status = U_ZERO_ERROR;
     Measure measures[] = {
         Measure(4.7, MeasureUnit::createHour(status), status),
-        Measure(23, MeasureUnit::createMinute(status), status),
-        Measure(16, MeasureUnit::createSecond(status), status)};
+        Measure(23.0, MeasureUnit::createMinute(status), status),
+        Measure(16.0, MeasureUnit::createSecond(status), status)};
     Locale en("en");
     NumberFormat *nf = NumberFormat::createInstance(en, status);
     MeasureFormat fmt("en", UMEASFMT_WIDTH_WIDE, nf, status);
@@ -1995,7 +1995,7 @@ void MeasureFormatTest::TestUnitPerUnitResolution() {
     UErrorCode status = U_ZERO_ERROR;
     Locale en("en");
     MeasureFormat fmt("en", UMEASFMT_WIDTH_SHORT, status);
-    Measure measure(50, MeasureUnit::createPound(status), status);
+    Measure measure(50.0, MeasureUnit::createPound(status), status);
     LocalPointer<MeasureUnit> sqInch(MeasureUnit::createSquareInch(status));
     if (!assertSuccess("Create of format unit and per unit", status)) {
         return;
@@ -2018,7 +2018,7 @@ void MeasureFormatTest::TestIndividualPluralFallback() {
     IcuTestErrorCode errorCode(*this, "TestIndividualPluralFallback");
     MeasureFormat mf("fr_CA", UMEASFMT_WIDTH_SHORT, errorCode);
     LocalPointer<Measure> twoDeg(
-        new Measure(2, MeasureUnit::createGenericTemperature(errorCode), errorCode), errorCode);
+        new Measure(2.0, MeasureUnit::createGenericTemperature(errorCode), errorCode), errorCode);
     UnicodeString expected = UNICODE_STRING_SIMPLE("2\\u00B0").unescape();
     UnicodeString actual;
     assertEquals("2 deg temp in fr_CA", expected, mf.format(twoDeg.orphan(), actual, errorCode), TRUE);
diff --git a/icu4c/source/test/intltest/numberformat2test.cpp b/icu4c/source/test/intltest/numberformat2test.cpp
index 71d00c8046a..2037cf944e0 100644
--- a/icu4c/source/test/intltest/numberformat2test.cpp
+++ b/icu4c/source/test/intltest/numberformat2test.cpp
@@ -321,7 +321,7 @@ void NumberFormat2Test::TestDigitListInterval() {
     DigitInterval result;
     DigitList digitList;
     {
-        digitList.set(12345);
+        digitList.set((int32_t)12345);
         verifyInterval(digitList.getSmallestInterval(result), 0, 5);
     }
     {
@@ -393,7 +393,7 @@ void NumberFormat2Test::TestQuantize() {
     DigitList digits;
     UErrorCode status = U_ZERO_ERROR;
     {
-        digits.set(1);
+        digits.set((int32_t)1);
         digits.quantize(quantity, status);
         verifyDigitList(".9996", digits);
     }
@@ -417,77 +417,77 @@ void NumberFormat2Test::TestQuantize() {
 void NumberFormat2Test::TestConvertScientificNotation() {
     DigitList digits;
     {
-        digits.set(186283);
+        digits.set((int32_t)186283);
         assertEquals("", 5, digits.toScientific(1, 1));
         verifyDigitList(
                 "1.86283",
                 digits);
     }
     {
-        digits.set(186283);
+        digits.set((int32_t)186283);
         assertEquals("", 0, digits.toScientific(6, 1));
         verifyDigitList(
                 "186283",
                 digits);
     }
     {
-        digits.set(186283);
+        digits.set((int32_t)186283);
         assertEquals("", -2, digits.toScientific(8, 1));
         verifyDigitList(
                 "18628300",
                 digits);
     }
     {
-        digits.set(43561);
+        digits.set((int32_t)43561);
         assertEquals("", 6, digits.toScientific(-1, 3));
         verifyDigitList(
                 ".043561",
                 digits);
     }
     {
-        digits.set(43561);
+        digits.set((int32_t)43561);
         assertEquals("", 3, digits.toScientific(0, 3));
         verifyDigitList(
                 "43.561",
                 digits);
     }
     {
-        digits.set(43561);
+        digits.set((int32_t)43561);
         assertEquals("", 3, digits.toScientific(2, 3));
         verifyDigitList(
                 "43.561",
                 digits);
     }
     {
-        digits.set(43561);
+        digits.set((int32_t)43561);
         assertEquals("", 0, digits.toScientific(3, 3));
         verifyDigitList(
                 "43561",
                 digits);
     }
     {
-        digits.set(43561);
+        digits.set((int32_t)43561);
         assertEquals("", 0, digits.toScientific(5, 3));
         verifyDigitList(
                 "43561",
                 digits);
     }
     {
-        digits.set(43561);
+        digits.set((int32_t)43561);
         assertEquals("", -3, digits.toScientific(6, 3));
         verifyDigitList(
                 "43561000",
                 digits);
     }
     {
-        digits.set(43561);
+        digits.set((int32_t)43561);
         assertEquals("", -3, digits.toScientific(8, 3));
         verifyDigitList(
                 "43561000",
                 digits);
     }
     {
-        digits.set(43561);
+        digits.set((int32_t)43561);
         assertEquals("", -6, digits.toScientific(9, 3));
         verifyDigitList(
                 "43561000000",
@@ -1456,19 +1456,19 @@ void NumberFormat2Test::TestAffixPattern() {
     second.remove();
     assertFalse("", second.iterator(iter).nextToken());
     assertTrue("", first.iterator(iter).nextToken());
-    assertEquals("", AffixPattern::kPercent, iter.getTokenType());
+    assertEquals("", (int32_t)AffixPattern::kPercent, iter.getTokenType());
     assertEquals("", 1, iter.getTokenLength());
     assertTrue("", iter.nextToken());
     UnicodeString str;
     assertEquals("", 500, iter.getLiteral(str).length());
-    assertEquals("", AffixPattern::kLiteral, iter.getTokenType());
+    assertEquals("", (int32_t)AffixPattern::kLiteral, iter.getTokenType());
     assertEquals("", 500, iter.getTokenLength());
     assertTrue("", iter.nextToken());
-    assertEquals("", AffixPattern::kCurrency, iter.getTokenType());
+    assertEquals("", (int32_t)AffixPattern::kCurrency, iter.getTokenType());
     assertEquals("", 2, iter.getTokenLength());
     assertTrue("", iter.nextToken());
     assertEquals("", 256, iter.getLiteral(str).length());
-    assertEquals("", AffixPattern::kLiteral, iter.getTokenType());
+    assertEquals("", (int32_t)AffixPattern::kLiteral, iter.getTokenType());
     assertEquals("", 256, iter.getTokenLength());
     assertFalse("", iter.nextToken());
 }
@@ -2534,7 +2534,7 @@ void NumberFormat2Test::TestPluralsAndRoundingScientific() {
                 expectedAttributes);
     }
     {
-        digits.set(-299792458);
+        digits.set(-299792458.0);
         NumberFormat2Test_Attributes expectedAttributes[] = {
             {UNUM_SIGN_FIELD, 0, 1},
             {UNUM_INTEGER_FIELD, 1, 2},
@@ -2555,7 +2555,7 @@ void NumberFormat2Test::TestPluralsAndRoundingScientific() {
     options.fExponent.fAlwaysShowSign = TRUE;
     precision.fMinExponentDigits = 3;
     {
-        digits.set(3);
+        digits.set(3.0);
         NumberFormat2Test_Attributes expectedAttributes[] = {
             {UNUM_INTEGER_FIELD, 0, 1},
             {UNUM_DECIMAL_SEPARATOR_FIELD, 1, 2},
@@ -2631,7 +2631,7 @@ void NumberFormat2Test::TestPluralsAndRoundingScientific() {
     precision.fMantissa.fMax.setIntDigitCount(1);
     precision.fMantissa.fMax.setFracDigitCount(2);
     {
-        digits.set(299792458);
+        digits.set((int32_t)299792458);
         verifyAffixesAndPadding(
                 "3.00E+008 Meters",
                 aap,
diff --git a/icu4c/source/test/intltest/numberformattesttuple.cpp b/icu4c/source/test/intltest/numberformattesttuple.cpp
index 7d458442242..46cfd0d0075 100644
--- a/icu4c/source/test/intltest/numberformattesttuple.cpp
+++ b/icu4c/source/test/intltest/numberformattesttuple.cpp
@@ -169,7 +169,7 @@ static void intToStr(
         x = -x;
     }
     if (neg) {
-        appendTo.append(0x2D);
+        appendTo.append((UChar)0x2D);
     }
     int32_t len = uprv_itou(buffer, UPRV_LENGTHOF(buffer), (uint32_t) x, 10, 1);
     appendTo.append(buffer, 0, len);
diff --git a/icu4c/source/test/intltest/pluralmaptest.cpp b/icu4c/source/test/intltest/pluralmaptest.cpp
index 111b15acaff..f89c568fdae 100644
--- a/icu4c/source/test/intltest/pluralmaptest.cpp
+++ b/icu4c/source/test/intltest/pluralmaptest.cpp
@@ -56,24 +56,24 @@ void PluralMapTest::runIndexedTest(int32_t index, UBool exec, const char* &name,
 }
 
 void PluralMapTest::TestToCategory() {
-    assertEquals("", PluralMapBase::OTHER, PluralMapBase::toCategory("other"));
-    assertEquals("", PluralMapBase::ZERO, PluralMapBase::toCategory("zero"));
-    assertEquals("", PluralMapBase::ONE, PluralMapBase::toCategory("one"));
-    assertEquals("", PluralMapBase::TWO, PluralMapBase::toCategory("two"));
-    assertEquals("", PluralMapBase::FEW, PluralMapBase::toCategory("few"));
-    assertEquals("", PluralMapBase::MANY, PluralMapBase::toCategory("many"));
-    assertEquals("", PluralMapBase::NONE, PluralMapBase::toCategory("Many"));
+    assertEquals("", (int32_t)PluralMapBase::OTHER, PluralMapBase::toCategory("other"));
+    assertEquals("", (int32_t)PluralMapBase::ZERO, PluralMapBase::toCategory("zero"));
+    assertEquals("", (int32_t)PluralMapBase::ONE, PluralMapBase::toCategory("one"));
+    assertEquals("", (int32_t)PluralMapBase::TWO, PluralMapBase::toCategory("two"));
+    assertEquals("", (int32_t)PluralMapBase::FEW, PluralMapBase::toCategory("few"));
+    assertEquals("", (int32_t)PluralMapBase::MANY, PluralMapBase::toCategory("many"));
+    assertEquals("", (int32_t)PluralMapBase::NONE, PluralMapBase::toCategory("Many"));
     assertEquals(
             "",
-            PluralMapBase::FEW,
+            (int32_t)PluralMapBase::FEW,
             PluralMapBase::toCategory(UnicodeString("few")));
     assertEquals(
             "",
-            PluralMapBase::MANY,
+            (int32_t)PluralMapBase::MANY,
             PluralMapBase::toCategory(UnicodeString("many")));
     assertEquals(
             "",
-            PluralMapBase::NONE,
+            (int32_t)PluralMapBase::NONE,
             PluralMapBase::toCategory(UnicodeString("Many")));
 }
 
@@ -117,24 +117,24 @@ void PluralMapTest::TestIterate() {
     PluralMapBase::Category index = PluralMapBase::NONE;
     const UnicodeString *current = map.next(index);
     assertEquals("", "pickles", *current);
-    assertEquals("", PluralMapBase::OTHER, index);
+    assertEquals("", (int32_t)PluralMapBase::OTHER, index);
     current = map.next(index);
     assertEquals("", "pickle", *current);
-    assertEquals("", PluralMapBase::ONE, index);
+    assertEquals("", (int32_t)PluralMapBase::ONE, index);
     current = map.next(index);
     assertEquals("", "picklefew", *current);
-    assertEquals("", PluralMapBase::FEW, index);
+    assertEquals("", (int32_t)PluralMapBase::FEW, index);
     current = map.next(index);
-    assertEquals("", PluralMapBase::CATEGORY_COUNT, index);
+    assertEquals("", (int32_t)PluralMapBase::CATEGORY_COUNT, index);
     assertTrue("", current == NULL);
 
     PluralMapForPluralMapTest map2;
     index = PluralMapBase::NONE;
     current = map2.next(index);
     assertEquals("", "", *current);
-    assertEquals("", PluralMapBase::OTHER, index);
+    assertEquals("", (int32_t)PluralMapBase::OTHER, index);
     current = map2.next(index);
-    assertEquals("", PluralMapBase::CATEGORY_COUNT, index);
+    assertEquals("", (int32_t)PluralMapBase::CATEGORY_COUNT, index);
     assertTrue("", current == NULL);
 }
 
diff --git a/icu4c/source/test/intltest/quantityformattertest.cpp b/icu4c/source/test/intltest/quantityformattertest.cpp
index a96e1f0e204..3f2b543f520 100644
--- a/icu4c/source/test/intltest/quantityformattertest.cpp
+++ b/icu4c/source/test/intltest/quantityformattertest.cpp
@@ -40,12 +40,12 @@ void QuantityFormatterTest::TestBasic() {
     assertFalse(
             "adding bad variant",
             fmt.addIfAbsent("a bad variant", "{0} pounds", status));
-    assertEquals("adding bad variant status", U_ILLEGAL_ARGUMENT_ERROR, status);
+    assertEquals("adding bad variant status", (int32_t)U_ILLEGAL_ARGUMENT_ERROR, status);
     status = U_ZERO_ERROR;
     assertFalse(
             "Adding bad pattern",
             fmt.addIfAbsent("other", "{0} {1} too many placeholders", status));
-    assertEquals("adding bad pattern status", U_ILLEGAL_ARGUMENT_ERROR, status);
+    assertEquals("adding bad pattern status", (int32_t)U_ILLEGAL_ARGUMENT_ERROR, status);
     status = U_ZERO_ERROR;
     assertFalse("isValid with no patterns", fmt.isValid());
     assertTrue(
@@ -121,9 +121,9 @@ void QuantityFormatterTest::TestBasic() {
         UnicodeString appendTo;
         assertEquals(
                 "format singular",
-                "1 pound",
+                UnicodeString("1 pound"),
                 fmt.format(
-                        1,
+                        1.0,
                         *numfmt,
                         *plurrule,
                         appendTo,
@@ -132,9 +132,9 @@ void QuantityFormatterTest::TestBasic() {
         appendTo.remove();
         assertEquals(
                 "format plural",
-                "2 pounds",
+                UnicodeString("2 pounds"),
                 fmt.format(
-                        2,
+                        2.0,
                         *numfmt,
                         *plurrule,
                         appendTo,
diff --git a/icu4c/source/test/intltest/reldatefmttest.cpp b/icu4c/source/test/intltest/reldatefmttest.cpp
index 08b0dcebba3..3a91f4cf045 100644
--- a/icu4c/source/test/intltest/reldatefmttest.cpp
+++ b/icu4c/source/test/intltest/reldatefmttest.cpp
@@ -714,10 +714,10 @@ void RelativeDateTimeFormatterTest::TestGetters() {
     // copy and assignment.
     RelativeDateTimeFormatter fmt2(fmt);
     fmt3 = fmt2;
-    assertEquals("style", UDAT_STYLE_NARROW, fmt3.getFormatStyle());
+    assertEquals("style", (int32_t)UDAT_STYLE_NARROW, fmt3.getFormatStyle());
     assertEquals(
             "context",
-            UDISPCTX_CAPITALIZATION_FOR_MIDDLE_OF_SENTENCE,
+            (int32_t)UDISPCTX_CAPITALIZATION_FOR_MIDDLE_OF_SENTENCE,
             fmt3.getCapitalizationContext());
     assertSuccess("", status);
 }
diff --git a/icu4c/source/test/intltest/simpleformattertest.cpp b/icu4c/source/test/intltest/simpleformattertest.cpp
index 03db517b7aa..f503f391946 100644
--- a/icu4c/source/test/intltest/simpleformattertest.cpp
+++ b/icu4c/source/test/intltest/simpleformattertest.cpp
@@ -90,10 +90,10 @@ void SimpleFormatterTest::TestNoArguments() {
 void SimpleFormatterTest::TestSyntaxErrors() {
     UErrorCode status = U_ZERO_ERROR;
     SimpleFormatter fmt("{}", status);
-    assertEquals("syntax error {}", U_ILLEGAL_ARGUMENT_ERROR, status);
+    assertEquals("syntax error {}", (int32_t)U_ILLEGAL_ARGUMENT_ERROR, status);
     status = U_ZERO_ERROR;
     fmt.applyPattern("{12d", status);
-    assertEquals("syntax error {12d", U_ILLEGAL_ARGUMENT_ERROR, status);
+    assertEquals("syntax error {12d", (int32_t)U_ILLEGAL_ARGUMENT_ERROR, status);
 }
 
 void SimpleFormatterTest::TestOneArgument() {
@@ -343,7 +343,7 @@ void SimpleFormatterTest::TestFormatReplaceNoOptimization() {
         return;
     }
     UnicodeString result("original");
-    int offsets[4];
+    int32_t offsets[4];
     UnicodeString freddy("freddy");
     UnicodeString frog("frog");
     UnicodeString by("by");
@@ -373,7 +373,7 @@ void SimpleFormatterTest::TestFormatReplaceNoOptimizationLeadingText() {
         return;
     }
     UnicodeString result("original");
-    int offsets[4];
+    int32_t offsets[4];
     UnicodeString freddy("freddy");
     UnicodeString frog("frog");
     UnicodeString by("by");
@@ -403,7 +403,7 @@ void SimpleFormatterTest::TestFormatReplaceOptimization() {
         return;
     }
     UnicodeString result("original");
-    int offsets[4];
+    int32_t offsets[4];
     UnicodeString freddy("freddy");
     UnicodeString frog("frog");
     UnicodeString by("by");
@@ -433,7 +433,7 @@ void SimpleFormatterTest::TestFormatReplaceNoOptimizationLeadingArgumentUsedTwic
         return;
     }
     UnicodeString result("original");
-    int offsets[4];
+    int32_t offsets[4];
     UnicodeString freddy("freddy");
     UnicodeString frog("frog");
     UnicodeString by("by");
diff --git a/icu4c/source/test/intltest/tzfmttst.cpp b/icu4c/source/test/intltest/tzfmttst.cpp
index 6a369dc6f72..dadcb544ec4 100644
--- a/icu4c/source/test/intltest/tzfmttst.cpp
+++ b/icu4c/source/test/intltest/tzfmttst.cpp
@@ -410,7 +410,7 @@ struct LocaleData {
         numDone = 0;
     }
 
-    UBool nextTest(int &rLocaleIndex, int &rPatternIndex) {
+    UBool nextTest(int32_t &rLocaleIndex, int32_t &rPatternIndex) {
         Mutex lock;
         if (patternIndex >= UPRV_LENGTHOF(PATTERNS) - 1) {
             if (localeIndex >= nLocales - 1) {
diff --git a/icu4c/source/test/testdata/encoded.utf16be b/icu4c/source/test/testdata/encoded.utf16be
index 93cd9555260..dffb747c677 100644
Binary files a/icu4c/source/test/testdata/encoded.utf16be and b/icu4c/source/test/testdata/encoded.utf16be differ