21984440 has 32 divisors (see below), whose sum is σ = 50168160. Its totient is φ = 8668800.

The previous prime is 21984421. The next prime is 21984449. The reversal of 21984440 is 4448912.

It is a super-2 number, since 2×21984440² = 966631204227200, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21984397 and 21984406.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21984449) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1031 + ... + 6710.

It is an arithmetic number, because the mean of its divisors is an integer number (1567755).

Almost surely, 2^21984440 is an apocalyptic number.

21984440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21984440 is an abundant number, since it is smaller than the sum of its proper divisors (28183720).

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

21984440 is a wasteful number, since it uses less digits than its factorization.

21984440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7823 (or 7819 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 32.

The square root of 21984440 is about 4688.7567648578. The cubic root of 21984440 is about 280.1378572852.

The spelling of 21984440 in words is "twenty-one million, nine hundred eighty-four thousand, four hundred forty".