21365968 has 40 divisors (see below), whose sum is σ = 44962400. Its totient is φ = 9777024.

The previous prime is 21365947. The next prime is 21365987. The reversal of 21365968 is 86956312.

It is a self number, because there is not a number n which added to its sum of digits gives 21365968.

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, 28543 + ... + 29281.

It is an arithmetic number, because the mean of its divisors is an integer number (1124060).

Almost surely, 2^21365968 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 21365968, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22481200).

21365968 is an abundant number, since it is smaller than the sum of its proper divisors (23596432).

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

21365968 is a wasteful number, since it uses less digits than its factorization.

21365968 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 899 (or 893 counting only the distinct ones).

The product of its digits is 77760, while the sum is 40.

The square root of 21365968 is about 4622.3336097690. Note that the first 3 decimals coincide. The cubic root of 21365968 is about 277.4858602757.

The spelling of 21365968 in words is "twenty-one million, three hundred sixty-five thousand, nine hundred sixty-eight".