21972665 has 32 divisors (see below), whose sum is σ = 31449600. Its totient is φ = 14526720.

The previous prime is 21972661. The next prime is 21972667. The reversal of 21972665 is 56627912.

It is a happy number.

It is not a de Polignac number, because 21972665 - 2² = 21972661 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21972661) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 56291 + ... + 56679.

It is an arithmetic number, because the mean of its divisors is an integer number (982800).

Almost surely, 2^21972665 is an apocalyptic number.

It is an amenable number.

21972665 is a deficient number, since it is larger than the sum of its proper divisors (9476935).

21972665 is a wasteful number, since it uses less digits than its factorization.

21972665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 497.

The product of its digits is 45360, while the sum is 38.

The square root of 21972665 is about 4687.5009333332. The cubic root of 21972665 is about 280.0878338389.

The spelling of 21972665 in words is "twenty-one million, nine hundred seventy-two thousand, six hundred sixty-five".