21979656 has 48 divisors (see below), whose sum is σ = 62665200. Its totient is φ = 6940512.

The previous prime is 21979631. The next prime is 21979663. The reversal of 21979656 is 65697912.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6666 + ... + 9401.

It is an arithmetic number, because the mean of its divisors is an integer number (1305525).

Almost surely, 2^21979656 is an apocalyptic number.

It is an amenable number.

21979656 is an abundant number, since it is smaller than the sum of its proper divisors (40685544).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21979656 is a wasteful number, since it uses less digits than its factorization.

21979656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16098 (or 16091 counting only the distinct ones).

The product of its digits is 204120, while the sum is 45.

The square root of 21979656 is about 4688.2465805459. The cubic root of 21979656 is about 280.1175356891.

The spelling of 21979656 in words is "twenty-one million, nine hundred seventy-nine thousand, six hundred fifty-six".