21398868 has 72 divisors (see below), whose sum is σ = 56784000. Its totient is φ = 6785856.

The previous prime is 21398849. The next prime is 21398873. The reversal of 21398868 is 86889312.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 107433 + ... + 107631.

It is a vampire number, since it can be written as 2388 ⋅ 8961 (with its own digits).

Almost surely, 2^21398868 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21398868, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28392000).

21398868 is an abundant number, since it is smaller than the sum of its proper divisors (35385132).

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

21398868 is a wasteful number, since it uses less digits than its factorization.

21398868 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 341 (or 336 counting only the distinct ones).

The product of its digits is 165888, while the sum is 45.

The square root of 21398868 is about 4625.8910493007. The cubic root of 21398868 is about 277.6282144305.

The spelling of 21398868 in words is "twenty-one million, three hundred ninety-eight thousand, eight hundred sixty-eight".