21565065 has 16 divisors (see below), whose sum is σ = 34736256. Its totient is φ = 11424000.

The previous prime is 21564989. The next prime is 21565073. The reversal of 21565065 is 56056512.

It is not a de Polignac number, because 21565065 - 2¹² = 21560969 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2496 + ... + 7025.

It is an arithmetic number, because the mean of its divisors is an integer number (2171016).

Almost surely, 2^21565065 is an apocalyptic number.

It is an amenable number.

21565065 is a deficient number, since it is larger than the sum of its proper divisors (13171191).

21565065 is a wasteful number, since it uses less digits than its factorization.

21565065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9680.

The product of its (nonzero) digits is 9000, while the sum is 30.

The square root of 21565065 is about 4643.8200869543. The cubic root of 21565065 is about 278.3451064936.

The spelling of 21565065 in words is "twenty-one million, five hundred sixty-five thousand, sixty-five".