21564423 has 6 divisors (see below), whose sum is σ = 31148624. Its totient is φ = 14376276.

The previous prime is 21564407. The next prime is 21564427. The reversal of 21564423 is 32446512.

21564423 is a `hidden beast` number, since 2 + 15 + 644 + 2 + 3 = 666.

It is not a de Polignac number, because 21564423 - 2⁴ = 21564407 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21564427) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1198015 + ... + 1198032.

Almost surely, 2^21564423 is an apocalyptic number.

21564423 is a deficient number, since it is larger than the sum of its proper divisors (9584201).

21564423 is a wasteful number, since it uses less digits than its factorization.

21564423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2396053 (or 2396050 counting only the distinct ones).

The product of its digits is 5760, while the sum is 27.

The square root of 21564423 is about 4643.7509623148. The cubic root of 21564423 is about 278.3423443204.

The spelling of 21564423 in words is "twenty-one million, five hundred sixty-four thousand, four hundred twenty-three".