That question is a bit unspecific :D

>NUMBER = atoi(argv[1]);

argv is populated at runtime based on what the OS passed you.

But you are right if you meant that my statement is too strong: you can't do arbitrary loop unrolling. You can jump to a loop that's unrolled once if the number is even, etc.

There are certainly also optimizers that will just output the input without any loop, but that's beyond anything I would expect of a current production compiler.