21156872 has 32 divisors (see below), whose sum is σ = 45161280. Its totient is φ = 9197760.

The previous prime is 21156871. The next prime is 21156901. The reversal of 21156872 is 27865112.

It is a super-2 number, since 2×21156872² = 895226465648768, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21156871) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3203 + ... + 7250.

It is an arithmetic number, because the mean of its divisors is an integer number (1411290).

Almost surely, 2^21156872 is an apocalyptic number.

21156872 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

21156872 is an abundant number, since it is smaller than the sum of its proper divisors (24004408).

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

21156872 is a wasteful number, since it uses less digits than its factorization.

21156872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10493 (or 10489 counting only the distinct ones).

The product of its digits is 6720, while the sum is 32.

The square root of 21156872 is about 4599.6599874339. The cubic root of 21156872 is about 276.5776949763.

The spelling of 21156872 in words is "twenty-one million, one hundred fifty-six thousand, eight hundred seventy-two".