21668368 has 20 divisors (see below), whose sum is σ = 42061420. Its totient is φ = 10813824.

The previous prime is 21668327. The next prime is 21668389. The reversal of 21668368 is 86386612.

It can be written as a sum of positive squares in 2 ways, for example, as 17539344 + 4129024 = 4188^2 + 2032^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21668368.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11218 + ... + 13006.

It is an arithmetic number, because the mean of its divisors is an integer number (2103071).

Almost surely, 2^21668368 is an apocalyptic number.

It is an amenable number.

21668368 is a deficient number, since it is larger than the sum of its proper divisors (20393052).

21668368 is a wasteful number, since it uses less digits than its factorization.

21668368 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2554 (or 2548 counting only the distinct ones).

The product of its digits is 82944, while the sum is 40.

The square root of 21668368 is about 4654.9294301847. The cubic root of 21668368 is about 278.7888503164.

The spelling of 21668368 in words is "twenty-one million, six hundred sixty-eight thousand, three hundred sixty-eight".