21256864 has 24 divisors (see below), whose sum is σ = 42270228. Its totient is φ = 10521600.

The previous prime is 21256847. The next prime is 21256867. The reversal of 21256864 is 46865212.

It can be written as a sum of positive squares in 2 ways, for example, as 13749264 + 7507600 = 3708^2 + 2740^2 .

It is a super-2 number, since 2×21256864² = 903708534228992, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21256867) 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, 57 + ... + 6520.

Almost surely, 2^21256864 is an apocalyptic number.

It is an amenable number.

21256864 is a deficient number, since it is larger than the sum of its proper divisors (21013364).

21256864 is a wasteful number, since it uses less digits than its factorization.

21256864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6688 (or 6680 counting only the distinct ones).

The product of its digits is 23040, while the sum is 34.

The square root of 21256864 is about 4610.5166738664. The cubic root of 21256864 is about 277.0127325404.

The spelling of 21256864 in words is "twenty-one million, two hundred fifty-six thousand, eight hundred sixty-four".