Construct 7

Computation Mode — Your opponents can't cast spells with converted mana costs that are prime numbers. (One is not prime.)

Your opponents can't block with creatures with converted mana costs that are prime numbers.

"A wise artithmetican once said the primes were the most lonesome of numbers. To that I say bollocks! 2, 3, 5, 7, 11, 13, 17, 19, 23, 31 ... and so on to eternity."
— Crude Scrawling