21565268 has 12 divisors (see below), whose sum is σ = 37772532. Its totient is φ = 10773120.

The previous prime is 21565261. The next prime is 21565273. The reversal of 21565268 is 86256512.

It can be written as a sum of positive squares in 2 ways, for example, as 753424 + 20811844 = 868^2 + 4562^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21565261) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 5996 + ... + 8892.

It is an arithmetic number, because the mean of its divisors is an integer number (3147711).

Almost surely, 2^21565268 is an apocalyptic number.

It is an amenable number.

21565268 is a deficient number, since it is larger than the sum of its proper divisors (16207264).

21565268 is a wasteful number, since it uses less digits than its factorization.

21565268 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4762 (or 4760 counting only the distinct ones).

The product of its digits is 28800, while the sum is 35.

The square root of 21565268 is about 4643.8419439081. The cubic root of 21565268 is about 278.3459798796.

It can be divided in two parts, 21 and 565268, that multiplied together give a triangular number (11870628 = T₄₈₇₂).

The spelling of 21565268 in words is "twenty-one million, five hundred sixty-five thousand, two hundred sixty-eight".