21564845 has 4 divisors (see below), whose sum is σ = 25877820. Its totient is φ = 17251872.

The previous prime is 21564793. The next prime is 21564929. The reversal of 21564845 is 54846512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7382089 + 14182756 = 2717^2 + 3766^2 .

It is a cyclic number.

It is not a de Polignac number, because 21564845 - 2¹⁰ = 21563821 is a prime.

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, 2156480 + ... + 2156489.

It is an arithmetic number, because the mean of its divisors is an integer number (6469455).

Almost surely, 2^21564845 is an apocalyptic number.

It is an amenable number.

21564845 is a deficient number, since it is larger than the sum of its proper divisors (4312975).

21564845 is an equidigital number, since it uses as much as digits as its factorization.

21564845 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4312974.

The product of its digits is 38400, while the sum is 35.

The square root of 21564845 is about 4643.7963994990. The cubic root of 21564845 is about 278.3441599607.

The spelling of 21564845 in words is "twenty-one million, five hundred sixty-four thousand, eight hundred forty-five".