21117972 has 24 divisors (see below), whose sum is σ = 50608096. Its totient is φ = 6848928.

The previous prime is 21117959. The next prime is 21117983. The reversal of 21117972 is 27971112.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 23338 + ... + 24225.

Almost surely, 2^21117972 is an apocalyptic number.

It is an amenable number.

21117972 is an abundant number, since it is smaller than the sum of its proper divisors (29490124).

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

21117972 is a wasteful number, since it uses less digits than its factorization.

21117972 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47607 (or 47605 counting only the distinct ones).

The product of its digits is 1764, while the sum is 30.

The square root of 21117972 is about 4595.4294685045. The cubic root of 21117972 is about 276.4080814814.

The spelling of 21117972 in words is "twenty-one million, one hundred seventeen thousand, nine hundred seventy-two".