21456656 has 40 divisors (see below), whose sum is σ = 45830400. Its totient is φ = 9668736.

The previous prime is 21456641. The next prime is 21456667. The reversal of 21456656 is 65665412.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7745 + ... + 10143.

It is an arithmetic number, because the mean of its divisors is an integer number (1145760).

Almost surely, 2^21456656 is an apocalyptic number.

21456656 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 21456656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22915200).

21456656 is an abundant number, since it is smaller than the sum of its proper divisors (24373744).

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

21456656 is a wasteful number, since it uses less digits than its factorization.

21456656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2463 (or 2457 counting only the distinct ones).

The product of its digits is 43200, while the sum is 35.

The square root of 21456656 is about 4632.1329860012. The cubic root of 21456656 is about 277.8779030106.

The spelling of 21456656 in words is "twenty-one million, four hundred fifty-six thousand, six hundred fifty-six".