21959665 has 48 divisors (see below), whose sum is σ = 34659072. Its totient is φ = 13003776.

The previous prime is 21959659. The next prime is 21959677. The reversal of 21959665 is 56695912.

It is not a de Polignac number, because 21959665 - 2³ = 21959657 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 131412 + ... + 131578.

It is an arithmetic number, because the mean of its divisors is an integer number (722064).

Almost surely, 2^21959665 is an apocalyptic number.

It is an amenable number.

21959665 is a deficient number, since it is larger than the sum of its proper divisors (12699407).

21959665 is a wasteful number, since it uses less digits than its factorization.

21959665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 226 (or 209 counting only the distinct ones).

The product of its digits is 145800, while the sum is 43.

The square root of 21959665 is about 4686.1140617787. The cubic root of 21959665 is about 280.0325854934.

The spelling of 21959665 in words is "twenty-one million, nine hundred fifty-nine thousand, six hundred sixty-five".