21717924 has 24 divisors (see below), whose sum is σ = 51854880. Its totient is φ = 7070784.

The previous prime is 21717919. The next prime is 21717937. The reversal of 21717924 is 42971712.

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, 20529 + ... + 21560.

It is an arithmetic number, because the mean of its divisors is an integer number (2160620).

Almost surely, 2^21717924 is an apocalyptic number.

It is an amenable number.

21717924 is an abundant number, since it is smaller than the sum of its proper divisors (30136956).

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

21717924 is a wasteful number, since it uses less digits than its factorization.

21717924 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42139 (or 42137 counting only the distinct ones).

The product of its digits is 7056, while the sum is 33.

The square root of 21717924 is about 4660.2493495520. The cubic root of 21717924 is about 279.0012204312.

The spelling of 21717924 in words is "twenty-one million, seven hundred seventeen thousand, nine hundred twenty-four".