By default, all strings of digits are parsed as base 10 numbers, including those with a leading zero. Numbers with a prefix 0b, 0o, 0d or 0x are parsed as binary, octal, decimal or hexadecimal respectively.
Additionally, there are built-in adverbial prefix operators to parse strings of "digits" of radix 2 through radix 36 into decimal. They will fail with a runtime error if they are fed a digit that is not valid in that radix.