21668688 has 40 divisors (see below), whose sum is σ = 62198400. Its totient is φ = 7222752.

The previous prime is 21668681. The next prime is 21668711. The reversal of 21668688 is 88686612.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21668681) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 24648 + ... + 25511.

It is an arithmetic number, because the mean of its divisors is an integer number (1554960).

Almost surely, 2^21668688 is an apocalyptic number.

It is an amenable number.

21668688 is an abundant number, since it is smaller than the sum of its proper divisors (40529712).

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

21668688 is a wasteful number, since it uses less digits than its factorization.

21668688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50176 (or 50164 counting only the distinct ones).

The product of its digits is 221184, while the sum is 45.

The square root of 21668688 is about 4654.9638022223. The cubic root of 21668688 is about 278.7902227009.

The spelling of 21668688 in words is "twenty-one million, six hundred sixty-eight thousand, six hundred eighty-eight".