21564764 has 12 divisors (see below), whose sum is σ = 40641384. Its totient is φ = 9952944.

The previous prime is 21564757. The next prime is 21564779. The reversal of 21564764 is 46746512.

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 3 ways as a sum of consecutive naturals, for example, 207302 + ... + 207405.

It is an arithmetic number, because the mean of its divisors is an integer number (3386782).

Almost surely, 2^21564764 is an apocalyptic number.

It is an amenable number.

21564764 is a deficient number, since it is larger than the sum of its proper divisors (19076620).

21564764 is a wasteful number, since it uses less digits than its factorization.

21564764 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 414724 (or 414722 counting only the distinct ones).

The product of its digits is 40320, while the sum is 35.

The square root of 21564764 is about 4643.7876781782. The cubic root of 21564764 is about 278.3438114629.

The spelling of 21564764 in words is "twenty-one million, five hundred sixty-four thousand, seven hundred sixty-four".