Converts an integer to its string representation, optionally in a given base.
$ wo 'IntegerString[255]'
255
$ wo 'IntegerString[255, 16]'
ff
Works on arbitrary-precision integers (beyond i128):
$ wo 'IntegerString[143207491493571284560146904872817600361573129, 2]'
110011010111111000011111110001111001100111000001111110111010000100011110001111110101101100100110010000011001000110000001111101000101010101100001001
$ wo 'IntegerString[-143207491493571284560146904872817600361573129, 2]'
110011010111111000011111110001111001100111000001111110111010000100011110001111110101101100100110010000011001000110000001111101000101010101100001001