21536564 has 24 divisors (see below), whose sum is σ = 43323840. Its totient is φ = 9176256.

The previous prime is 21536563. The next prime is 21536573. The reversal of 21536564 is 46563512.

It is a self number, because there is not a number n which added to its sum of digits gives 21536564.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21536561) 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, 2864 + ... + 7160.

It is an arithmetic number, because the mean of its divisors is an integer number (1805160).

Almost surely, 2^21536564 is an apocalyptic number.

It is an amenable number.

21536564 is an abundant number, since it is smaller than the sum of its proper divisors (21787276).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21536564 is a wasteful number, since it uses less digits than its factorization.

21536564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4487 (or 4485 counting only the distinct ones).

The product of its digits is 21600, while the sum is 32.

The square root of 21536564 is about 4640.7503703604. The cubic root of 21536564 is about 278.2224295108. Note that the first 3 decimals are identical.

The spelling of 21536564 in words is "twenty-one million, five hundred thirty-six thousand, five hundred sixty-four".