Hm... 32, eh? That's
2×2×2×2×2. Just for amusement,
3×3×3×3×3 is 243, whereas Abraham himself only lived to 170. Two is a very
odd prime, you know, the way its powers pack so closely together that way and other things...
There's a nifty thing about primes — from Fermat's
little theorem
np≡n(modp) we have a factorization
xp−x≡x(x+1)(x+2)⋯(x+p−1)(modp) which in particular gives
(p−1)!≡−1(modp); on the other hand, if
q is a composite number, then
q=pN for some minimal prime
p and some
N which is not smaller than
p. That is, either
p=2 and
N=2, or
2<N ; in the first case,
pN=2×2=4 and
3!=6≡2(mod4); in all other cases, we have one of
p<N or
2<p=N<2p<3p≤q, both of which lead to
q=pN|(q−1)!, so that the full repertoire of
(q−1)!(modq) is :
−1, if
q is prime ;
2, if
q=4;
0 otherwise. The odd case out,
q=4, highlights in a number-theory way just how odd the thickness of powers of
2 really is. It also arises as a
thing in my research, the natural operations in homotopy... but never mind that for now! It's my Birthday, and I think I'll have a sleep.