@DIGITS

@DIGITS[n]:  Returns 1 if the string is composed of decimal digits only, otherwise it returns 0. The Decimal character, the Thousands character, and the sign characters (+ or -) are not digits, and if they are present in the string @DIGITS will return 0.

Examples:

echo %@digits[12345]

echo %@digits[-12345]

echo %@digits[1.2345]