21572865 has 16 divisors (see below), whose sum is σ = 38352000. Its totient is φ = 11505456.

The previous prime is 21572849. The next prime is 21572867. The reversal of 21572865 is 56827512.

It is a happy number.

21572865 is a `hidden beast` number, since 2 + 1 + 572 + 86 + 5 = 666.

It is not a de Polignac number, because 21572865 - 2⁴ = 21572849 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21572867) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 79765 + ... + 80034.

It is an arithmetic number, because the mean of its divisors is an integer number (2397000).

Almost surely, 2^21572865 is an apocalyptic number.

It is an amenable number.

21572865 is a deficient number, since it is larger than the sum of its proper divisors (16779135).

21572865 is a wasteful number, since it uses less digits than its factorization.

21572865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 159813 (or 159807 counting only the distinct ones).

The product of its digits is 33600, while the sum is 36.

The square root of 21572865 is about 4644.6598368449. The cubic root of 21572865 is about 278.3786612286.

The spelling of 21572865 in words is "twenty-one million, five hundred seventy-two thousand, eight hundred sixty-five".