21731872 has 24 divisors (see below), whose sum is σ = 44646336. Its totient is φ = 10393152.

The previous prime is 21731869. The next prime is 21731891. The reversal of 21731872 is 27813712.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14028 + ... + 15499.

It is an arithmetic number, because the mean of its divisors is an integer number (1860264).

Almost surely, 2^21731872 is an apocalyptic number.

It is an amenable number.

21731872 is an abundant number, since it is smaller than the sum of its proper divisors (22914464).

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

21731872 is a wasteful number, since it uses less digits than its factorization.

21731872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29560 (or 29552 counting only the distinct ones).

The product of its digits is 4704, while the sum is 31.

The square root of 21731872 is about 4661.7455958042. The cubic root of 21731872 is about 279.0609357188.

The spelling of 21731872 in words is "twenty-one million, seven hundred thirty-one thousand, eight hundred seventy-two".