21616256 has 32 divisors (see below), whose sum is σ = 43532580. Its totient is φ = 10690560.

The previous prime is 21616241. The next prime is 21616279. The reversal of 21616256 is 65261612.

It can be written as a sum of positive squares in 2 ways, for example, as 18318400 + 3297856 = 4280^2 + 1816^2 .

It is a tau number, because it is divible by the number of its divisors (32).

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11546 + ... + 13286.

Almost surely, 2^21616256 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 21616256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21766290).

21616256 is an abundant number, since it is smaller than the sum of its proper divisors (21916324).

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

21616256 is an equidigital number, since it uses as much as digits as its factorization.

21616256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1852 (or 1840 counting only the distinct ones).

The product of its digits is 4320, while the sum is 29.

The square root of 21616256 is about 4649.3285536731. The cubic root of 21616256 is about 278.5651770051.

Adding to 21616256 its reverse (65261612), we get a palindrome (86877868).

The spelling of 21616256 in words is "twenty-one million, six hundred sixteen thousand, two hundred fifty-six".