21756872 has 16 divisors (see below), whose sum is σ = 43194060. Its totient is φ = 10238464.

The previous prime is 21756863. The next prime is 21756883. The reversal of 21756872 is 27865712.

It can be written as a sum of positive squares in 2 ways, for example, as 20921476 + 835396 = 4574^2 + 914^2 .

It is a super-2 number, since 2×21756872² = 946722958448768, which contains 22 as substring.

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, 79853 + ... + 80124.

Almost surely, 2^21756872 is an apocalyptic number.

It is an amenable number.

21756872 is a deficient number, since it is larger than the sum of its proper divisors (21437188).

21756872 is a wasteful number, since it uses less digits than its factorization.

21756872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 160000 (or 159996 counting only the distinct ones).

The product of its digits is 47040, while the sum is 38.

The square root of 21756872 is about 4664.4262240923. The cubic root of 21756872 is about 279.1679037989.

The spelling of 21756872 in words is "twenty-one million, seven hundred fifty-six thousand, eight hundred seventy-two".