21326564 has 36 divisors (see below), whose sum is σ = 44255484. Its totient is φ = 8963136.

The previous prime is 21326563. The next prime is 21326573. The reversal of 21326564 is 46562312.

It can be written as a sum of positive squares in 2 ways, for example, as 13249600 + 8076964 = 3640^2 + 2842^2 .

It is not an unprimeable number, because it can be changed into a prime (21326561) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9362 + ... + 11414.

It is an arithmetic number, because the mean of its divisors is an integer number (1229319).

Almost surely, 2^21326564 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21326564, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22127742).

21326564 is an abundant number, since it is smaller than the sum of its proper divisors (22928920).

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

21326564 is a wasteful number, since it uses less digits than its factorization.

21326564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2124 (or 2115 counting only the distinct ones).

The product of its digits is 8640, while the sum is 29.

The square root of 21326564 is about 4618.0692935468. The cubic root of 21326564 is about 277.3151716770.

Adding to 21326564 its reverse (46562312), we get a palindrome (67888876).

The spelling of 21326564 in words is "twenty-one million, three hundred twenty-six thousand, five hundred sixty-four".