21818856 has 16 divisors (see below), whose sum is σ = 54547200. Its totient is φ = 7272944.

The previous prime is 21818851. The next prime is 21818861. The reversal of 21818856 is 65881812.

It is an interprime number because it is at equal distance from previous prime (21818851) and next prime (21818861).

It is not an unprimeable number, because it can be changed into a prime (21818851) 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, 454536 + ... + 454583.

It is an arithmetic number, because the mean of its divisors is an integer number (3409200).

Almost surely, 2^21818856 is an apocalyptic number.

It is an amenable number.

21818856 is an abundant number, since it is smaller than the sum of its proper divisors (32728344).

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

21818856 is a wasteful number, since it uses less digits than its factorization.

21818856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 909128 (or 909124 counting only the distinct ones).

The product of its digits is 30720, while the sum is 39.

The square root of 21818856 is about 4671.0658312638. The cubic root of 21818856 is about 279.4327632064.

The spelling of 21818856 in words is "twenty-one million, eight hundred eighteen thousand, eight hundred fifty-six".