@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]
1
echo %@digits[-12345]
0
echo %@digits[1.2345]
0