21867856 has 20 divisors (see below), whose sum is σ = 43830900. Its totient is φ = 10556672.

The previous prime is 21867823. The next prime is 21867869. The reversal of 21867856 is 65876812.

It can be written as a sum of positive squares in 2 ways, for example, as 3549456 + 18318400 = 1884^2 + 4280^2 .

It is a congruent number.

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, 23101 + ... + 24028.

It is an arithmetic number, because the mean of its divisors is an integer number (2191545).

Almost surely, 2^21867856 is an apocalyptic number.

It is an amenable number.

21867856 is an abundant number, since it is smaller than the sum of its proper divisors (21963044).

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

21867856 is a wasteful number, since it uses less digits than its factorization.

21867856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47166 (or 47160 counting only the distinct ones).

The product of its digits is 161280, while the sum is 43.

The square root of 21867856 is about 4676.3079453774. The cubic root of 21867856 is about 279.6417868195.

The spelling of 21867856 in words is "twenty-one million, eight hundred sixty-seven thousand, eight hundred fifty-six".