Prove that if p and q are odd primes and q divides (2^p)-1, then q=2pk+1 for some integer k.
I can't find any clue on this one...
Any help is appreciated!
[also under discussion in math links forum]
I can also show that a product of two factors of the form 2pk+1 is of the same form (i.e. the product is of the form 2pm+1 for some integer m).
So by induction, we can say that ANY divisor(not necessarily prime) of (2^p)-1 is also of the form 2pk+1? Am I right?