21564045 has 12 divisors (see below), whose sum is σ = 37377756. Its totient is φ = 11500800.

The previous prime is 21564029. The next prime is 21564061. The reversal of 21564045 is 54046512.

21564045 is a `hidden beast` number, since 2 + 15 + 640 + 4 + 5 = 666.

It is an interprime number because it is at equal distance from previous prime (21564029) and next prime (21564061).

It can be written as a sum of positive squares in 2 ways, for example, as 10614564 + 10949481 = 3258^2 + 3309^2 .

It is not a de Polignac number, because 21564045 - 2⁴ = 21564029 is a prime.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 239556 + ... + 239645.

It is an arithmetic number, because the mean of its divisors is an integer number (3114813).

Almost surely, 2^21564045 is an apocalyptic number.

It is an amenable number.

21564045 is a deficient number, since it is larger than the sum of its proper divisors (15813711).

21564045 is a wasteful number, since it uses less digits than its factorization.

21564045 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 479212 (or 479209 counting only the distinct ones).

The product of its (nonzero) digits is 4800, while the sum is 27.

The square root of 21564045 is about 4643.7102622795. The cubic root of 21564045 is about 278.3407179685.

The spelling of 21564045 in words is "twenty-one million, five hundred sixty-four thousand, forty-five".