21687968 has 24 divisors (see below), whose sum is σ = 44946720. Its totient is φ = 10272960.

The previous prime is 21687959. The next prime is 21687997. The reversal of 21687968 is 86978612.

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, 17228 + ... + 18443.

It is an arithmetic number, because the mean of its divisors is an integer number (1872780).

Almost surely, 2^21687968 is an apocalyptic number.

It is an amenable number.

21687968 is an abundant number, since it is smaller than the sum of its proper divisors (23258752).

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

21687968 is a wasteful number, since it uses less digits than its factorization.

21687968 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35700 (or 35692 counting only the distinct ones).

The product of its digits is 290304, while the sum is 47.

The square root of 21687968 is about 4657.0342493909. The cubic root of 21687968 is about 278.8728839446.

The spelling of 21687968 in words is "twenty-one million, six hundred eighty-seven thousand, nine hundred sixty-eight".