21506564 has 24 divisors (see below), whose sum is σ = 41586048. Its totient is φ = 9680000.

The previous prime is 21506533. The next prime is 21506593. The reversal of 21506564 is 46560512.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5312 + ... + 8439.

It is an arithmetic number, because the mean of its divisors is an integer number (1732752).

Almost surely, 2^21506564 is an apocalyptic number.

It is an amenable number.

21506564 is a deficient number, since it is larger than the sum of its proper divisors (20079484).

21506564 is a wasteful number, since it uses less digits than its factorization.

21506564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13795 (or 13793 counting only the distinct ones).

The product of its (nonzero) digits is 7200, while the sum is 29.

The square root of 21506564 is about 4637.5170080551. The cubic root of 21506564 is about 278.0931833991.

The spelling of 21506564 in words is "twenty-one million, five hundred six thousand, five hundred sixty-four".