21913857 has 24 divisors (see below), whose sum is σ = 36863424. Its totient is φ = 12284064.

The previous prime is 21913849. The next prime is 21913861. The reversal of 21913857 is 75831912.

It is not a de Polignac number, because 21913857 - 2³ = 21913849 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21913817) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 58 + ... + 6620.

It is an arithmetic number, because the mean of its divisors is an integer number (1535976).

Almost surely, 2^21913857 is an apocalyptic number.

It is an amenable number.

21913857 is a deficient number, since it is larger than the sum of its proper divisors (14949567).

21913857 is a wasteful number, since it uses less digits than its factorization.

21913857 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6629 (or 6626 counting only the distinct ones).

The product of its digits is 15120, while the sum is 36.

The square root of 21913857 is about 4681.2238784318. The cubic root of 21913857 is about 279.8377333618.

The spelling of 21913857 in words is "twenty-one million, nine hundred thirteen thousand, eight hundred fifty-seven".