21566368 has 48 divisors (see below), whose sum is σ = 45360000. Its totient is φ = 10063872.

The previous prime is 21566351. The next prime is 21566371. The reversal of 21566368 is 86366512.

It is a super-2 number, since 2×21566368² = 930216457422848, which contains 22 as substring.

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, 47808 + ... + 48256.

It is an arithmetic number, because the mean of its divisors is an integer number (945000).

Almost surely, 2^21566368 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 21566368, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22680000).

21566368 is an abundant number, since it is smaller than the sum of its proper divisors (23793632).

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

21566368 is a wasteful number, since it uses less digits than its factorization.

21566368 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 557 (or 549 counting only the distinct ones).

The product of its digits is 51840, while the sum is 37.

The square root of 21566368 is about 4643.9603788146. The cubic root of 21566368 is about 278.3507124180.

The spelling of 21566368 in words is "twenty-one million, five hundred sixty-six thousand, three hundred sixty-eight".