21398256 has 200 divisors, whose sum is σ = 72019200. Its totient is φ = 6065280.

The previous prime is 21398239. The next prime is 21398261. The reversal of 21398256 is 65289312.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21398256.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 270825 + ... + 270903.

It is an arithmetic number, because the mean of its divisors is an integer number (360096).

Almost surely, 2^21398256 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 21398256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36009600).

21398256 is an abundant number, since it is smaller than the sum of its proper divisors (50620944).

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

21398256 is a wasteful number, since it uses less digits than its factorization.

21398256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129 (or 114 counting only the distinct ones).

The product of its digits is 25920, while the sum is 36.

The square root of 21398256 is about 4625.8248994098. The cubic root of 21398256 is about 277.6255677160.

The spelling of 21398256 in words is "twenty-one million, three hundred ninety-eight thousand, two hundred fifty-six".