21393968 has 20 divisors (see below), whose sum is σ = 42788928. Its totient is φ = 10351680.

The previous prime is 21393961. The next prime is 21393989. The reversal of 21393968 is 86939312.

21393968 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (21393961) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21071 + ... + 22062.

Almost surely, 2^21393968 is an apocalyptic number.

It is an amenable number.

21393968 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21393968 is a wasteful number, since it uses less digits than its factorization.

21393968 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43172 (or 43166 counting only the distinct ones).

The product of its digits is 69984, while the sum is 41.

The square root of 21393968 is about 4625.3613912861. The cubic root of 21393968 is about 277.6070219996.

The spelling of 21393968 in words is "twenty-one million, three hundred ninety-three thousand, nine hundred sixty-eight".