The printed representation of an integer consists of a sequence of digits, optionally prefixed by a sign and arbitrarily separated by commas or underscores.
Integers are entered in base 10 unless prefixed with a base-changing prefix. 0x
begins a hexadecimal literal, 0o
an octal literal, and 0b
a binary literal. A sign, if any, goes before the base prefix.
More information on integers can be found in Integers