21689568 has 72 divisors (see below), whose sum is σ = 62270208. Its totient is φ = 7160832.

The previous prime is 21689557. The next prime is 21689573. The reversal of 21689568 is 86598612.

21689568 is a `hidden beast` number, since 2 + 1 + 6 + 89 + 568 = 666.

It is a tau number, because it is divible by the number of its divisors (72).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 36280 + ... + 36872.

It is an arithmetic number, because the mean of its divisors is an integer number (864864).

Almost surely, 2^21689568 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 21689568, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31135104).

21689568 is an abundant number, since it is smaller than the sum of its proper divisors (40580640).

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

21689568 is a wasteful number, since it uses less digits than its factorization.

21689568 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 736 (or 725 counting only the distinct ones).

The product of its digits is 207360, while the sum is 45.

The square root of 21689568 is about 4657.2060293700. The cubic root of 21689568 is about 278.8797415971.

The spelling of 21689568 in words is "twenty-one million, six hundred eighty-nine thousand, five hundred sixty-eight".