composite number Pumping Lemma for L = {$0^p$∣$p$ is a composite number} Consider the language $L = \{0^p \mid p \text{ is a composite number}\}$.

I know that this is not a regular language. I have thought that to prove this language is not regular take the complement (prime numbers) which must be regular, but its complement has prime numbers and 0 and 1 occurrences of 0's.

Could anybody give me a hint to prove without taking complement?
The Pumping Lemma will give you a way to generate strings in the language whose lengths are in an arithmetic progression.  If you pick the initial string right, you should be able to apply Dirichlet's (?) Theorem that arithmetic progressions having certain properties necessarily include infinitely many primes.