21315856 has 20 divisors (see below), whose sum is σ = 41766300. Its totient is φ = 10537472.

The previous prime is 21315823. The next prime is 21315883. The reversal of 21315856 is 65851312.

It can be written as a sum of positive squares in 2 ways, for example, as 1245456 + 20070400 = 1116^2 + 4480^2 .

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 3 ways as a sum of consecutive naturals, for example, 6061 + ... + 8908.

It is an arithmetic number, because the mean of its divisors is an integer number (2088315).

Almost surely, 2^21315856 is an apocalyptic number.

It is an amenable number.

21315856 is a deficient number, since it is larger than the sum of its proper divisors (20450444).

21315856 is a wasteful number, since it uses less digits than its factorization.

21315856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15066 (or 15060 counting only the distinct ones).

The product of its digits is 7200, while the sum is 31.

The square root of 21315856 is about 4616.9097890256. The cubic root of 21315856 is about 277.2687508848.

The spelling of 21315856 in words is "twenty-one million, three hundred fifteen thousand, eight hundred fifty-six".