21617256 has 16 divisors (see below), whose sum is σ = 54043200. Its totient is φ = 7205744.

The previous prime is 21617249. The next prime is 21617273. The reversal of 21617256 is 65271612.

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, 450336 + ... + 450383.

It is an arithmetic number, because the mean of its divisors is an integer number (3377700).

Almost surely, 2^21617256 is an apocalyptic number.

It is an amenable number.

21617256 is an abundant number, since it is smaller than the sum of its proper divisors (32425944).

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

21617256 is a wasteful number, since it uses less digits than its factorization.

21617256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 900728 (or 900724 counting only the distinct ones).

The product of its digits is 5040, while the sum is 30.

The square root of 21617256 is about 4649.4360948399. The cubic root of 21617256 is about 278.5694725513.

Adding to 21617256 its reverse (65271612), we get a palindrome (86888868).

The spelling of 21617256 in words is "twenty-one million, six hundred seventeen thousand, two hundred fifty-six".