21565715 has 16 divisors (see below), whose sum is σ = 26638848. Its totient is φ = 16752096.

The previous prime is 21565699. The next prime is 21565721. The reversal of 21565715 is 51756512.

It is a cyclic number.

It is not a de Polignac number, because 21565715 - 2⁴ = 21565699 is a prime.

It is a super-2 number, since 2×21565715² = 930160126922450, which contains 22 as substring.

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, 38024 + ... + 38586.

It is an arithmetic number, because the mean of its divisors is an integer number (1664928).

Almost surely, 2^21565715 is an apocalyptic number.

21565715 is a deficient number, since it is larger than the sum of its proper divisors (5073133).

21565715 is a wasteful number, since it uses less digits than its factorization.

21565715 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 778.

The product of its digits is 10500, while the sum is 32.

The square root of 21565715 is about 4643.8900719117. The cubic root of 21565715 is about 278.3479030305.

The spelling of 21565715 in words is "twenty-one million, five hundred sixty-five thousand, seven hundred fifteen".