What's happening to an int that starts with 0? ex 00101 [duplicate]

Answer 1

Then the integer is treated as an octal number. So,

01001

equals

1 * 8 ^ 0 + 0 * 8 ^ 1 + 0 * 8 ^ 2 + 1 * 8 ^ 3 = 1 + 0 + 0 + 512 = 513

No magic in there.