20856564 has 36 divisors (see below), whose sum is σ = 53513824. Its totient is φ = 6847632.

The previous prime is 20856551. The next prime is 20856599. The reversal of 20856564 is 46565802.

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1912 + ... + 6735.

Almost surely, 2^20856564 is an apocalyptic number.

It is an amenable number.

20856564 is an abundant number, since it is smaller than the sum of its proper divisors (32657260).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20856564 is a wasteful number, since it uses less digits than its factorization.

20856564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8724 (or 8719 counting only the distinct ones).

The product of its (nonzero) digits is 57600, while the sum is 36.

The square root of 20856564 is about 4566.8987288969. The cubic root of 20856564 is about 275.2628407119.

It can be divided in two parts, 2085 and 6564, that added together give a square (8649 = 93²).

The spelling of 20856564 in words is "twenty million, eight hundred fifty-six thousand, five hundred sixty-four".