21500564 has 12 divisors (see below), whose sum is σ = 38543988. Its totient is φ = 10488000.

The previous prime is 21500543. The next prime is 21500587. The reversal of 21500564 is 46500512.

It can be written as a sum of positive squares in 2 ways, for example, as 4443664 + 17056900 = 2108^2 + 4130^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 65387 + ... + 65714.

It is an arithmetic number, because the mean of its divisors is an integer number (3211999).

Almost surely, 2^21500564 is an apocalyptic number.

It is an amenable number.

21500564 is a deficient number, since it is larger than the sum of its proper divisors (17043424).

21500564 is a wasteful number, since it uses less digits than its factorization.

21500564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 131146 (or 131144 counting only the distinct ones).

The product of its (nonzero) digits is 1200, while the sum is 23.

The square root of 21500564 is about 4636.8700650331. The cubic root of 21500564 is about 278.0673197559.

The spelling of 21500564 in words is "twenty-one million, five hundred thousand, five hundred sixty-four".