21120256 has 72 divisors (see below), whose sum is σ = 46799424. Its totient is φ = 9461760.

The previous prime is 21120251. The next prime is 21120257. The reversal of 21120256 is 65202112.

21120256 is nontrivially palindromic in base 15.

It is a hoax number, since the sum of its digits (19) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21120251) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 99991 + ... + 100201.

It is an arithmetic number, because the mean of its divisors is an integer number (649992).

Almost surely, 2^21120256 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 21120256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23399712).

21120256 is an abundant number, since it is smaller than the sum of its proper divisors (25679168).

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

21120256 is a wasteful number, since it uses less digits than its factorization.

21120256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 267 (or 253 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 19.

The square root of 21120256 is about 4595.6779695710. The cubic root of 21120256 is about 276.4180460320.

Adding to 21120256 its reverse (65202112), we get a palindrome (86322368).

The spelling of 21120256 in words is "twenty-one million, one hundred twenty thousand, two hundred fifty-six".