In mathematics, a semiprime is a natural number that is the product of two prime numbers. The two primes in the product may equal each other, so the semiprimes include the squares of prime numbers.Because there are infinitely many prime numbers, there are also infinitely many semiprimes. Semiprimes are also called biprimes. In mathematics, a semiprime is a natural number that is the product of two prime numbers. The two primes in the product may equal each other, so the semiprimes include the squares of prime numbers.Because there are infinitely many prime numbers, there are also infinitely many semiprimes. Semiprimes are also called biprimes.