21564522 has 64 divisors (see below), whose sum is σ = 55468800. Its totient is φ = 6082560.

The previous prime is 21564511. The next prime is 21564523. The reversal of 21564522 is 22546512.

21564522 is a `hidden beast` number, since 2 + 15 + 645 + 2 + 2 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21564523) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 33322 + ... + 33962.

It is an arithmetic number, because the mean of its divisors is an integer number (866700).

Almost surely, 2^21564522 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21564522, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27734400).

21564522 is an abundant number, since it is smaller than the sum of its proper divisors (33904278).

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

21564522 is a wasteful number, since it uses less digits than its factorization.

21564522 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 748 (or 742 counting only the distinct ones).

The product of its digits is 4800, while the sum is 27.

The square root of 21564522 is about 4643.7616217890. The cubic root of 21564522 is about 278.3427702666.

The spelling of 21564522 in words is "twenty-one million, five hundred sixty-four thousand, five hundred twenty-two".