21856256 has 64 divisors (see below), whose sum is σ = 47185200. Its totient is φ = 10092544.

The previous prime is 21856253. The next prime is 21856267. The reversal of 21856256 is 65265812.

It is a tau number, because it is divible by the number of its divisors (64).

It is a super-3 number, since 3×21856256³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21856253) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 753650 + ... + 753678.

Almost surely, 2^21856256 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 21856256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23592600).

21856256 is an abundant number, since it is smaller than the sum of its proper divisors (25328944).

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

21856256 is an frugal number, since it uses more digits than its factorization.

21856256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82 (or 54 counting only the distinct ones).

The product of its digits is 28800, while the sum is 35.

The square root of 21856256 is about 4675.0674861439. The cubic root of 21856256 is about 279.5923319107.

The spelling of 21856256 in words is "twenty-one million, eight hundred fifty-six thousand, two hundred fifty-six".