21564801 has 24 divisors (see below), whose sum is σ = 32242496. Its totient is φ = 13880160.

The previous prime is 21564793. The next prime is 21564929. The reversal of 21564801 is 10846512.

21564801 is a `hidden beast` number, since 2 + 15 + 648 + 0 + 1 = 666.

It is not a de Polignac number, because 21564801 - 2³ = 21564793 is a prime.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21564001) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 39591 + ... + 40131.

Almost surely, 2^21564801 is an apocalyptic number.

It is an amenable number.

21564801 is a deficient number, since it is larger than the sum of its proper divisors (10677695).

21564801 is a wasteful number, since it uses less digits than its factorization.

21564801 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 693 (or 690 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The square root of 21564801 is about 4643.7916619935. The cubic root of 21564801 is about 278.3439706533.

The spelling of 21564801 in words is "twenty-one million, five hundred sixty-four thousand, eight hundred one".