21064564 has 24 divisors (see below), whose sum is σ = 39590208. Its totient is φ = 9770880.

The previous prime is 21064553. The next prime is 21064567. The reversal of 21064564 is 46546012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21064567) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2647 + ... + 7009.

It is an arithmetic number, because the mean of its divisors is an integer number (1649592).

Almost surely, 2^21064564 is an apocalyptic number.

It is an amenable number.

21064564 is a deficient number, since it is larger than the sum of its proper divisors (18525644).

21064564 is a wasteful number, since it uses less digits than its factorization.

21064564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4455 (or 4453 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 28.

The square root of 21064564 is about 4589.6147986514. The cubic root of 21064564 is about 276.1748699277.

It can be divided in two parts, 2106 and 4564, that added together give a triangular number (6670 = T₁₁₅).

The spelling of 21064564 in words is "twenty-one million, sixty-four thousand, five hundred sixty-four".