diff --git a/src/AbstractRule.php b/src/AbstractRule.php
index e3ec532..90cd2c8 100644
--- a/src/AbstractRule.php
+++ b/src/AbstractRule.php
@@ -37,6 +37,14 @@ protected function shortname(): string
         return strtolower((new ReflectionClass($this))->getShortName());
     }
 
+    /**
+     * Determine if input chars are only numbers.
+     */
+    protected function isOnlyNumericCharacters(string $value): bool
+    {
+        return preg_match("/^[0-9]+$/", $value) === 1;
+    }
+
     /**
      * Return localized error message.
      */
diff --git a/src/Rules/AustrianInsuranceNumber.php b/src/Rules/AustrianInsuranceNumber.php
index 3a1b094..a17a165 100644
--- a/src/Rules/AustrianInsuranceNumber.php
+++ b/src/Rules/AustrianInsuranceNumber.php
@@ -33,7 +33,7 @@ public function isValid(mixed $value): bool
     {
         $value = str_replace(' ', '', (string) $value);
 
-        return is_numeric($value)
+        return $this->isOnlyNumericCharacters($value)
             && $this->startsNotWithZero($value)
             && $this->hasValidLength($value)
             && $this->hasValidBirthday($value)
diff --git a/src/Rules/Ean.php b/src/Rules/Ean.php
index bce0068..7b94714 100644
--- a/src/Rules/Ean.php
+++ b/src/Rules/Ean.php
@@ -26,7 +26,11 @@ public function __construct(private array $lengths = [8, 13])
      */
     public function isValid(mixed $value): bool
     {
-        return is_numeric($value) && $this->hasAllowedLength($value) && $this->checksumMatches($value);
+        $value = strval($value);
+
+        return $this->isOnlyNumericCharacters($value)
+            && $this->hasAllowedLength($value)
+            && $this->checksumMatches($value);
     }
 
     /**
diff --git a/src/Rules/Gtin.php b/src/Rules/Gtin.php
index fabbbc7..2164f8f 100644
--- a/src/Rules/Gtin.php
+++ b/src/Rules/Gtin.php
@@ -31,7 +31,9 @@ public function __construct(private array $lengths = [8, 12, 13, 14])
      */
     public function isValid(mixed $value): bool
     {
-        if (!is_numeric($value)) {
+        $value = strval($value);
+
+        if (!$this->isOnlyNumericCharacters($value)) {
             return false;
         }
 
@@ -39,8 +41,6 @@ public function isValid(mixed $value): bool
             return false;
         }
 
-        $value = strval($value);
-
         return match (strlen($value)) {
             8, 13 => parent::isValid($value),
             12 => parent::checksumMatches('0' . $value),
diff --git a/tests/Rules/EanTest.php b/tests/Rules/EanTest.php
index c343ed6..477e839 100644
--- a/tests/Rules/EanTest.php
+++ b/tests/Rules/EanTest.php
@@ -68,6 +68,7 @@ public static function dataProviderEan13(): Generator
         yield [false, '40123455'];
         yield [false, '96385074'];
         yield [false, '65833254'];
+        yield [false, '004.03996E+12'];
     }
 
     public static function dataProviderEan8(): Generator