21564725 has 24 divisors (see below), whose sum is σ = 32914560. Its totient is φ = 13648320.

The previous prime is 21564713. The next prime is 21564733. The reversal of 21564725 is 52746512.

It is not a de Polignac number, because 21564725 - 2²⁰ = 20516149 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21564691 and 21564700.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2465 + ... + 7014.

It is an arithmetic number, because the mean of its divisors is an integer number (1371440).

Almost surely, 2^21564725 is an apocalyptic number.

21564725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21564725 is a deficient number, since it is larger than the sum of its proper divisors (11349835).

21564725 is a wasteful number, since it uses less digits than its factorization.

21564725 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9509 (or 9504 counting only the distinct ones).

The product of its digits is 16800, while the sum is 32.

The square root of 21564725 is about 4643.7834790179. The cubic root of 21564725 is about 278.3436436673.

The spelling of 21564725 in words is "twenty-one million, five hundred sixty-four thousand, seven hundred twenty-five".