[Blackadder]

Originally Posted by science_man_88

no number divisible by a number other than 1 or itself is prime. Now, 2^p-2 = 2(2^p-1-1) therefore is divisible by 2

there is only one exception: when p-1 = 1 (and p=2) -- 2^p-1-1 = 1 doesn't hurt primality.

That makes sense. Thank you.