21891056 has 40 divisors (see below), whose sum is σ = 47876400. Its totient is φ = 9605120.

The previous prime is 21891047. The next prime is 21891061. The reversal of 21891056 is 65019812.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2960 + ... + 7248.

It is an arithmetic number, because the mean of its divisors is an integer number (1196910).

Almost surely, 2^21891056 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 21891056, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23938200).

21891056 is an abundant number, since it is smaller than the sum of its proper divisors (25985344).

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

21891056 is a wasteful number, since it uses less digits than its factorization.

21891056 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4337 (or 4331 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 32.

The square root of 21891056 is about 4678.7878772178. The cubic root of 21891056 is about 279.7406441942.

The spelling of 21891056 in words is "twenty-one million, eight hundred ninety-one thousand, fifty-six".