21397968 has 60 divisors (see below), whose sum is σ = 63414468. Its totient is φ = 6712320.

The previous prime is 21397949. The next prime is 21397997. The reversal of 21397968 is 86979312.

It can be written as a sum of positive squares in 2 ways, for example, as 10188864 + 11209104 = 3192^2 + 3348^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1923 + ... + 6818.

Almost surely, 2^21397968 is an apocalyptic number.

It is an amenable number.

21397968 is an abundant number, since it is smaller than the sum of its proper divisors (42016500).

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

21397968 is a wasteful number, since it uses less digits than its factorization.

21397968 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8772 (or 8763 counting only the distinct ones).

The product of its digits is 163296, while the sum is 45.

The square root of 21397968 is about 4625.7937697221. The cubic root of 21397968 is about 277.6243221858.

The spelling of 21397968 in words is "twenty-one million, three hundred ninety-seven thousand, nine hundred sixty-eight".