21715856 has 20 divisors (see below), whose sum is σ = 42361500. Its totient is φ = 10783872.

The previous prime is 21715853. The next prime is 21715861. The reversal of 21715856 is 65851712.

It can be written as a sum of positive squares in 2 ways, for example, as 2496400 + 19219456 = 1580^2 + 4384^2 .

It is a hoax number, since the sum of its digits (35) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21715853) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2171 + ... + 6938.

It is an arithmetic number, because the mean of its divisors is an integer number (2118075).

Almost surely, 2^21715856 is an apocalyptic number.

It is an amenable number.

21715856 is a deficient number, since it is larger than the sum of its proper divisors (20645644).

21715856 is a wasteful number, since it uses less digits than its factorization.

21715856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9266 (or 9260 counting only the distinct ones).

The product of its digits is 16800, while the sum is 35.

The square root of 21715856 is about 4660.0274677302. The cubic root of 21715856 is about 278.9923645688.

The spelling of 21715856 in words is "twenty-one million, seven hundred fifteen thousand, eight hundred fifty-six".