21565228 has 24 divisors (see below), whose sum is σ = 40804400. Its totient is φ = 9937728.

The previous prime is 21565199. The next prime is 21565261. The reversal of 21565228 is 82256512.

It is a self number, because there is not a number n which added to its sum of digits gives 21565228.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1023 + ... + 6646.

Almost surely, 2^21565228 is an apocalyptic number.

It is an amenable number.

21565228 is a deficient number, since it is larger than the sum of its proper divisors (19239172).

21565228 is a wasteful number, since it uses less digits than its factorization.

21565228 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7729 (or 7727 counting only the distinct ones).

The product of its digits is 9600, while the sum is 31.

The square root of 21565228 is about 4643.8376371273. The cubic root of 21565228 is about 278.3458077843.

The spelling of 21565228 in words is "twenty-one million, five hundred sixty-five thousand, two hundred twenty-eight".