21851256 has 96 divisors (see below), whose sum is σ = 67346640. Its totient is φ = 5870592.

The previous prime is 21851251. The next prime is 21851257. The reversal of 21851256 is 65215812.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21851251) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 19446 + ... + 20538.

Almost surely, 2^21851256 is an apocalyptic number.

21851256 is the 2499-th nonagonal number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21851256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33673320).

21851256 is an abundant number, since it is smaller than the sum of its proper divisors (45495384).

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

21851256 is a wasteful number, since it uses less digits than its factorization.

21851256 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1133 (or 1122 counting only the distinct ones).

The product of its digits is 4800, while the sum is 30.

The square root of 21851256 is about 4674.5327039181. The cubic root of 21851256 is about 279.5710097429.

The spelling of 21851256 in words is "twenty-one million, eight hundred fifty-one thousand, two hundred fifty-six".