21979623 has 16 divisors (see below), whose sum is σ = 31124736. Its totient is φ = 13749120.

The previous prime is 21979621. The next prime is 21979631. The reversal of 21979623 is 32697912.

It is not a de Polignac number, because 21979623 - 2¹ = 21979621 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21979621) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 31840 + ... + 32522.

It is an arithmetic number, because the mean of its divisors is an integer number (1945296).

Almost surely, 2^21979623 is an apocalyptic number.

21979623 is a deficient number, since it is larger than the sum of its proper divisors (9145113).

21979623 is a wasteful number, since it uses less digits than its factorization.

21979623 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1334.

The product of its digits is 40824, while the sum is 39.

The square root of 21979623 is about 4688.2430611051. The cubic root of 21979623 is about 280.1173955006.

The spelling of 21979623 in words is "twenty-one million, nine hundred seventy-nine thousand, six hundred twenty-three".