21856356 has 72 divisors (see below), whose sum is σ = 59439744. Its totient is φ = 6746880.

The previous prime is 21856349. The next prime is 21856357. The reversal of 21856356 is 65365812.

21856356 is a `hidden beast` number, since 2 + 18 + 5 + 635 + 6 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21856356.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21856357) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 43201 + ... + 43703.

It is an arithmetic number, because the mean of its divisors is an integer number (825552).

Almost surely, 2^21856356 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21856356, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29719872).

21856356 is an abundant number, since it is smaller than the sum of its proper divisors (37583388).

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

21856356 is a wasteful number, since it uses less digits than its factorization.

21856356 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 601 (or 596 counting only the distinct ones).

The product of its digits is 43200, while the sum is 36.

The square root of 21856356 is about 4675.0781811645. The cubic root of 21856356 is about 279.5927583209.

The spelling of 21856356 in words is "twenty-one million, eight hundred fifty-six thousand, three hundred fifty-six".