About the numbers with p divisors, where p is prime: Yes, the numbers with 3 divisors are the squares of primes. More generally; if p is prime then the n-th number with p divisors is equal to the n-th prime raised to power p-1. Cf. A000040, A001248, A030514, A030516, A030629, A030631, A030635, A030637, etc. Best regards, Omar E. Pol