21672565 has 16 divisors (see below), whose sum is σ = 27578880. Its totient is φ = 16320960.

The previous prime is 21672527. The next prime is 21672571. The reversal of 21672565 is 56527612.

It is not a de Polignac number, because 21672565 - 2¹³ = 21664373 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a self number, because there is not a number n which added to its sum of digits gives 21672565.

It is a congruent number.

It is an unprimeable number.

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, 3846 + ... + 7624.

It is an arithmetic number, because the mean of its divisors is an integer number (1723680).

Almost surely, 2^21672565 is an apocalyptic number.

It is an amenable number.

21672565 is a deficient number, since it is larger than the sum of its proper divisors (5906315).

21672565 is a wasteful number, since it uses less digits than its factorization.

21672565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3852.

The product of its digits is 25200, while the sum is 34.

The square root of 21672565 is about 4655.3802207768. The cubic root of 21672565 is about 278.8068489226.

The spelling of 21672565 in words is "twenty-one million, six hundred seventy-two thousand, five hundred sixty-five".