21331457 has 4 divisors (see below), whose sum is σ = 24378816. Its totient is φ = 18284100.

The previous prime is 21331451. The next prime is 21331459. The reversal of 21331457 is 75413312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21331457 - 2⁸ = 21331201 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21331451) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1523669 + ... + 1523682.

It is an arithmetic number, because the mean of its divisors is an integer number (6094704).

Almost surely, 2^21331457 is an apocalyptic number.

It is an amenable number.

21331457 is a deficient number, since it is larger than the sum of its proper divisors (3047359).

21331457 is an equidigital number, since it uses as much as digits as its factorization.

21331457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3047358.

The product of its digits is 2520, while the sum is 26.

The square root of 21331457 is about 4618.5990300090. The cubic root of 21331457 is about 277.3363783964.

Adding to 21331457 its reverse (75413312), we get a palindrome (96744769).

The spelling of 21331457 in words is "twenty-one million, three hundred thirty-one thousand, four hundred fifty-seven".