21156240 has 160 divisors (see below), whose sum is σ = 76780800. Its totient is φ = 4816896.

The previous prime is 21156227. The next prime is 21156241. The reversal of 21156240 is 4265112.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is not an unprimeable number, because it can be changed into a prime (21156241) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 82192 + ... + 82448.

It is an arithmetic number, because the mean of its divisors is an integer number (479880).

Almost surely, 2^21156240 is an apocalyptic number.

21156240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21156240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38390400).

21156240 is an abundant number, since it is smaller than the sum of its proper divisors (55624560).

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

21156240 is a wasteful number, since it uses less digits than its factorization.

21156240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 294 (or 274 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 21156240 is about 4599.5912861905. The cubic root of 21156240 is about 276.5749409642.

The spelling of 21156240 in words is "twenty-one million, one hundred fifty-six thousand, two hundred forty".