21255804 has 48 divisors (see below), whose sum is σ = 55703200. Its totient is φ = 7008768.

The previous prime is 21255799. The next prime is 21255821. The reversal of 21255804 is 40855212.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a plaindrome in base 16.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9462 + ... + 11490.

Almost surely, 2^21255804 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 21255804, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27851600).

21255804 is an abundant number, since it is smaller than the sum of its proper divisors (34447396).

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

21255804 is a wasteful number, since it uses less digits than its factorization.

21255804 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2139 (or 2131 counting only the distinct ones).

The product of its (nonzero) digits is 3200, while the sum is 27.

The square root of 21255804 is about 4610.4017178550. The cubic root of 21255804 is about 277.0081279356.

The spelling of 21255804 in words is "twenty-one million, two hundred fifty-five thousand, eight hundred four".