diff --git a/packages/core/src/integer.ts b/packages/core/src/integer.ts
index b04c6f866..458871e78 100644
--- a/packages/core/src/integer.ts
+++ b/packages/core/src/integer.ts
@@ -956,6 +956,20 @@ class Integer {
   }
 }
 
+/**
+ * @private
+ * @param num
+ * @param radix
+ * @param minSize
+ * @returns {string}
+ */
+function _convertNumberToString (num: number, radix: number, minSize: number): string {
+  const theNumberString = num.toString(radix)
+  const paddingLength = Math.max(minSize - theNumberString.length, 0)
+  const padding = '0'.repeat(paddingLength)
+  return `${padding}${theNumberString}`
+}
+
 /**
  *
  * @private
@@ -967,7 +981,7 @@ class Integer {
 function _isValidNumberFromString (theString: string, theNumber: number, radix: number): boolean {
   return !Number.isNaN(theString) &&
     !Number.isNaN(theNumber) &&
-    theNumber.toString(radix).toLocaleLowerCase() === theString.toLocaleLowerCase()
+    _convertNumberToString(theNumber, radix, theString.length) === theString.toLowerCase()
 }
 
 type Integerable =
diff --git a/packages/core/test/integer.test.ts b/packages/core/test/integer.test.ts
index f76677b98..c135e20a7 100644
--- a/packages/core/test/integer.test.ts
+++ b/packages/core/test/integer.test.ts
@@ -309,6 +309,12 @@ describe('Integer', () => {
   test('int("7891123456789876a") not toThrow invalid character', () =>
     expect(() => int('7891123456789876a')).not.toThrow())
 
+  test.each(malformedNumbers())('int("%s", { strictStringValidation: true }) toThrow invalid character', (theNumberString) =>
+    expect(() => int(theNumberString, { strictStringValidation: true })).toThrow())
+
+  test.each(wellFormedNumbersAndRadix())('Integer.fromString("%s", %n, { strictStringValidation: true }) not toThrown', (theNumberString, radix) =>
+    expect(() => Integer.fromString(theNumberString, radix, { strictStringValidation: true })).not.toThrow())
+
   forEachStaticToNumberScenarios(({ input, expectedOutput }) =>
     test(`Integer.toNumber(${mayIntegerToString(input)}) toEqual ${expectedOutput}`, () =>
       expect(Integer.toNumber(input)).toEqual(expectedOutput))
@@ -1109,6 +1115,79 @@ function forEachStaticInSafeRangeScenarios (
   ].forEach(func)
 }
 
+function malformedNumbers (): string[] {
+  return [
+    '7a',
+    '7891123a',
+    '78911234a',
+    '789112345a',
+    '7891123456a',
+    '7891123456789876a',
+    '78911234567898765a',
+    '789112345678987654a',
+    '78911234567898765a2',
+    '7891123456789876a25',
+    '789112345678987a256',
+    '78911234567898a2567',
+    '7891123456789a25678',
+    '789112345678a256789',
+    '78911234567a2567898',
+    '7891123456a25678987',
+    '789112345a256789876',
+    '78911234a2567898765',
+    '7891123a25678987654',
+    '7891123ab2567898765',
+    '78911234ab256789876',
+    '789112345ab25678987',
+    '7891123456ab2567898',
+    '78911234567ab256789',
+    '78911234567abc25678',
+    '78911234567abcd2567',
+    '78911234567abcde256',
+    '78911234567abcdef25',
+    '78911234567abcdefg2',
+    '7891123456abcdefgh1',
+    '789112345abcdefgh12',
+    '78911234abcdefgh123',
+    '7891123abcdefgh1234',
+    '789112abcdefghij123',
+    '7kkkkabcdefghijklmn',
+    '7kkkkabcdefg12345mn',
+    '7kkkkabcdefg123456n',
+    '7kkkkab22efg123456n',
+    '7kkkkab22efg12345mn',
+    '7kkkkab223fg12345mn',
+    'kkkkk11223fg12345mn',
+    'kkkkk11223fg123456n',
+    'kkkkk11223fg1234567',
+    'kkkkk11223451234567',
+    'kkk111gkk3451234567',
+    'kkk111gkkkk51234567',
+    'kkk111gkkkkk123kk67',
+    'kkkk234',
+    'kkkk2345',
+    'kkkk23456',
+    'kkkk234567',
+    'kkkk2345679kk',
+    'kkkk2345679kkkkkk',
+    'kkk234567',
+    'kkk2345679',
+    'kk2345679',
+    'kkkkkkkkkkkkkkkkkkk'
+  ]
+}
+
+function wellFormedNumbersAndRadix (): Array<[string, number]> {
+  return [
+    ['01', 2],
+    ['012', 3],
+    ['0123', 4],
+    ['0123456789', 10],
+    ['0123456789ab', 12],
+    ['0123456789abCde', 16]
+  ]
+}
+
 interface AssertionPair<I, O> {
   input: I
   expectedOutput: O