Paul Erdös, the Arisen

This creature can only be cast from graveyards
{c}{c},Discard this card: Add {b}{b}{b}.
Paul Erdos enters the battlefield with X +1/+1 counters.
If X is prime, he has haste and indestructible.
{t}:Put an E counter on target creature, then add
one for each E counter on this creature.
It gets this ability.
Creatures with E counters get +7+7, as
well as -1/-1 for each E counter on them.