21715668 has 48 divisors (see below), whose sum is σ = 60634560. Its totient is φ = 6681312.

The previous prime is 21715663. The next prime is 21715679. The reversal of 21715668 is 86651712.

21715668 is a `hidden beast` number, since 21 + 71 + 566 + 8 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21715663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6330 + ... + 9137.

It is an arithmetic number, because the mean of its divisors is an integer number (1263220).

Almost surely, 2^21715668 is an apocalyptic number.

It is an amenable number.

21715668 is an abundant number, since it is smaller than the sum of its proper divisors (38918892).

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

21715668 is a wasteful number, since it uses less digits than its factorization.

21715668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15493 (or 15485 counting only the distinct ones).

The product of its digits is 20160, while the sum is 36.

The square root of 21715668 is about 4660.0072961316. The cubic root of 21715668 is about 278.9915594625.

The spelling of 21715668 in words is "twenty-one million, seven hundred fifteen thousand, six hundred sixty-eight".