21105564 has 12 divisors (see below), whose sum is σ = 49246344. Its totient is φ = 7035184.

The previous prime is 21105563. The next prime is 21105569. The reversal of 21105564 is 46550112.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21105563) 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, 879387 + ... + 879410.

It is an arithmetic number, because the mean of its divisors is an integer number (4103862).

Almost surely, 2^21105564 is an apocalyptic number.

It is an amenable number.

21105564 is an abundant number, since it is smaller than the sum of its proper divisors (28140780).

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

21105564 is a wasteful number, since it uses less digits than its factorization.

21105564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1758804 (or 1758802 counting only the distinct ones).

The product of its (nonzero) digits is 1200, while the sum is 24.

The square root of 21105564 is about 4594.0792330999. The cubic root of 21105564 is about 276.3539357613.

Adding to 21105564 its reverse (46550112), we get a palindrome (67655676).

The spelling of 21105564 in words is "twenty-one million, one hundred five thousand, five hundred sixty-four".