21761

21761 is a natural number that sits between 21760 and 21762. In number theory, it is notable for being the product of two primes: 47 and 463, so its prime factorization is 21761 = 47 × 463. This makes 21761 a semiprime, a type of composite number formed by exactly two prime factors.

Consequences of this factorization include its divisors: 1, 47, 463, and 21761. The total number of positive divisors is four. The sum of all divisors is (1+47)(1+463) = 48 × 464 = 22272, which yields a sum of proper divisors equal to 511; thus 21761 is not a perfect number. Because the two prime factors are distinct, 21761 is square-free.

Additional arithmetic observations include that 21761 is odd, and the sum of its digits is 17, so it is not divisible by 3 or 9. It is not a palindrome (its reverse is 16712). As a simple example of a semiprime, 21761 can be used to illustrate basic concepts in elementary number theory and the study of composite numbers formed by two primes.