21668668 has 24 divisors (see below), whose sum is σ = 45222912. Its totient is φ = 8882544.

The previous prime is 21668629. The next prime is 21668681. The reversal of 21668668 is 86686612.

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, 16180 + ... + 17467.

It is an arithmetic number, because the mean of its divisors is an integer number (1884288).

Almost surely, 2^21668668 is an apocalyptic number.

21668668 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21668668 is an abundant number, since it is smaller than the sum of its proper divisors (23554244).

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

21668668 is a wasteful number, since it uses less digits than its factorization.

21668668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33681 (or 33679 counting only the distinct ones).

The product of its digits is 165888, while the sum is 43.

The square root of 21668668 is about 4654.9616539774. The cubic root of 21668668 is about 278.7901369273.

The spelling of 21668668 in words is "twenty-one million, six hundred sixty-eight thousand, six hundred sixty-eight".