How many two digit numbers have exactly 4 positive factors? (Here 1 and the number $$n$$ are also considered as factors of $$n$$.)

A number has exactly four divisors when it is either $$p^3$$ or $$pq$$ for distinct primes $$p$$ and $$q$$. The two digit cubes of primes are $$27$$ and there are 29 two digit numbers that are a product of two distinct primes. Together this gives $$1 + 29 = 30$$ such numbers.