21662665 has 16 divisors (see below), whose sum is σ = 27381888. Its totient is φ = 16420096.

The previous prime is 21662653. The next prime is 21662671. The reversal of 21662665 is 56626612.

It is a cyclic number.

It is not a de Polignac number, because 21662665 - 2⁵ = 21662633 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21662665.

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, 12162 + ... + 13828.

It is an arithmetic number, because the mean of its divisors is an integer number (1711368).

Almost surely, 2^21662665 is an apocalyptic number.

It is an amenable number.

21662665 is a deficient number, since it is larger than the sum of its proper divisors (5719223).

21662665 is a wasteful number, since it uses less digits than its factorization.

21662665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1808.

The product of its digits is 25920, while the sum is 34.

The square root of 21662665 is about 4654.3168134539. The cubic root of 21662665 is about 278.7643895861.

The spelling of 21662665 in words is "twenty-one million, six hundred sixty-two thousand, six hundred sixty-five".