21568957 has 4 divisors (see below), whose sum is σ = 21628096. Its totient is φ = 21509820.

The previous prime is 21568949. The next prime is 21568973. The reversal of 21568957 is 75986512.

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 21568957 - 2³ = 21568949 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21568927) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 29019 + ... + 29752.

It is an arithmetic number, because the mean of its divisors is an integer number (5407024).

Almost surely, 2^21568957 is an apocalyptic number.

It is an amenable number.

21568957 is a deficient number, since it is larger than the sum of its proper divisors (59139).

21568957 is an equidigital number, since it uses as much as digits as its factorization.

21568957 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59138.

The product of its digits is 151200, while the sum is 43.

The square root of 21568957 is about 4644.2391195975. The cubic root of 21568957 is about 278.3618504572.

The spelling of 21568957 in words is "twenty-one million, five hundred sixty-eight thousand, nine hundred fifty-seven".