21564855 has 48 divisors (see below), whose sum is σ = 40674816. Its totient is φ = 10506240.

The previous prime is 21564793. The next prime is 21564929. The reversal of 21564855 is 55846512.

21564855 is a `hidden beast` number, since 2 + 1 + 5 + 648 + 5 + 5 = 666.

It is not a de Polignac number, because 21564855 - 2⁹ = 21564343 is a prime.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 111639 + ... + 111831.

It is an arithmetic number, because the mean of its divisors is an integer number (847392).

Almost surely, 2^21564855 is an apocalyptic number.

21564855 is a deficient number, since it is larger than the sum of its proper divisors (19109961).

21564855 is a wasteful number, since it uses less digits than its factorization.

21564855 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 408 (or 405 counting only the distinct ones).

The product of its digits is 48000, while the sum is 36.

The square root of 21564855 is about 4643.7974762041. The cubic root of 21564855 is about 278.3442029851.

The spelling of 21564855 in words is "twenty-one million, five hundred sixty-four thousand, eight hundred fifty-five".