21457

21457 is a natural number that follows 21456 and precedes 21458. In mathematics, it is classified as a composite number and specifically as a semiprime because it has exactly two prime factors, 43 and 499, both of which are primes. The prime factorization is 21457 = 43 × 499. It is odd, not divisible by 2, 3, or 5; its digital sum is 19, so it is not a multiple of 3.

In standard decimal notation it is 21457; in hexadecimal it is 0x53D1; in binary it is 101001111010001.

Positive divisors are 1, 43, 499, and 21457. The number is squarefree, since its prime factors are distinct.

As a semiprime, 21457 is of interest in discussions of factorization and primality testing, illustrating a product of two distinct primes. It does not have widely noted cultural, historical, or scientific significance beyond its mathematical properties.