21568440 has 32 divisors (see below), whose sum is σ = 64705680. Its totient is φ = 5751552.

The previous prime is 21568433. The next prime is 21568471. The reversal of 21568440 is 4486512.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 21568398 and 21568407.

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, 89749 + ... + 89988.

Almost surely, 2^21568440 is an apocalyptic number.

21568440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21568440 is an abundant number, since it is smaller than the sum of its proper divisors (43137240).

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

21568440 is a wasteful number, since it uses less digits than its factorization.

21568440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 179751 (or 179747 counting only the distinct ones).

The product of its (nonzero) digits is 7680, while the sum is 30.

The square root of 21568440 is about 4644.1834589086. The cubic root of 21568440 is about 278.3596263622.

The spelling of 21568440 in words is "twenty-one million, five hundred sixty-eight thousand, four hundred forty".