21904440 has 32 divisors (see below), whose sum is σ = 65713680. Its totient is φ = 5841152.

The previous prime is 21904433. The next prime is 21904451. The reversal of 21904440 is 4440912.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21904440.

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, 91149 + ... + 91388.

Almost surely, 2^21904440 is an apocalyptic number.

21904440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21904440 is an abundant number, since it is smaller than the sum of its proper divisors (43809240).

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

21904440 is a wasteful number, since it uses less digits than its factorization.

21904440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 182551 (or 182547 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 24.

The square root of 21904440 is about 4680.2179436432. The cubic root of 21904440 is about 279.7976429066.

The spelling of 21904440 in words is "twenty-one million, nine hundred four thousand, four hundred forty".