21572565 has 16 divisors (see below), whose sum is σ = 39447168. Its totient is φ = 9861696.

The previous prime is 21572563. The next prime is 21572567. The reversal of 21572565 is 56527512.

It is an interprime number because it is at equal distance from previous prime (21572563) and next prime (21572567).

It is not a de Polignac number, because 21572565 - 2¹ = 21572563 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21572563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 102622 + ... + 102831.

It is an arithmetic number, because the mean of its divisors is an integer number (2465448).

Almost surely, 2^21572565 is an apocalyptic number.

It is an amenable number.

21572565 is a deficient number, since it is larger than the sum of its proper divisors (17874603).

21572565 is a wasteful number, since it uses less digits than its factorization.

21572565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 205468.

The product of its digits is 21000, while the sum is 33.

The square root of 21572565 is about 4644.6275415796. The cubic root of 21572565 is about 278.3773708115.

The spelling of 21572565 in words is "twenty-one million, five hundred seventy-two thousand, five hundred sixty-five".