21056256 has 216 divisors, whose sum is σ = 70681520. Its totient is φ = 5971968.

The previous prime is 21056249. The next prime is 21056263. The reversal of 21056256 is 65265012.

It is an interprime number because it is at equal distance from previous prime (21056249) and next prime (21056263).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 569070 + ... + 569106.

Almost surely, 2^21056256 is an apocalyptic number.

21056256 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21056256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35340760).

21056256 is an abundant number, since it is smaller than the sum of its proper divisors (49625264).

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

21056256 is a wasteful number, since it uses less digits than its factorization.

21056256 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91 (or 74 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

The square root of 21056256 is about 4588.7096225410. The cubic root of 21056256 is about 276.1385567695.

It can be divided in two parts, 21056 and 256, that added together give a palindrome (21312).

The spelling of 21056256 in words is "twenty-one million, fifty-six thousand, two hundred fifty-six".