21840444 has 72 divisors (see below), whose sum is σ = 59125248. Its totient is φ = 6773760.

The previous prime is 21840433. The next prime is 21840457. The reversal of 21840444 is 44404812.

It is a happy number.

21840444 is a `hidden beast` number, since 218 + 4 + 0 + 444 = 666.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 77584 + ... + 77864.

It is an arithmetic number, because the mean of its divisors is an integer number (821184).

Almost surely, 2^21840444 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 21840444, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29562624).

21840444 is an abundant number, since it is smaller than the sum of its proper divisors (37284804).

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

21840444 is a wasteful number, since it uses less digits than its factorization.

21840444 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 435 (or 430 counting only the distinct ones).

The product of its (nonzero) digits is 4096, while the sum is 27.

The square root of 21840444 is about 4673.3760815924. The cubic root of 21840444 is about 279.5248915634.

The spelling of 21840444 in words is "twenty-one million, eight hundred forty thousand, four hundred forty-four".