A semiprime is a natural number that is the product of exactly two prime numbers. These prime numbers can be the same, which means a semiprime can be a perfect square of a prime. For example, the number 9 is a semiprime because it is the product of the prime number 3 multiplied by itself (3 × 3). Other examples include 6 (2 × 3) and 15 (3 × 5). Semiprimes are important in number theory and have applications in cryptography, particularly in algorithms like RSA. In this context, the difficulty of factoring large semiprimes into their prime components provides security for digital communications.