21855872 has 16 divisors (see below), whose sum is σ = 43541250. Its totient is φ = 10927872.

The previous prime is 21855839. The next prime is 21855877. The reversal of 21855872 is 27855812.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 15178816 + 6677056 = 3896^2 + 2584^2 .

It is a tau number, because it is divible by the number of its divisors (16).

It is not an unprimeable number, because it can be changed into a prime (21855877) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 85247 + ... + 85502.

Almost surely, 2^21855872 is an apocalyptic number.

It is an amenable number.

21855872 is a deficient number, since it is larger than the sum of its proper divisors (21685378).

21855872 is an equidigital number, since it uses as much as digits as its factorization.

21855872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 170763 (or 170751 counting only the distinct ones).

The product of its digits is 44800, while the sum is 38.

The square root of 21855872 is about 4675.0264170377. The cubic root of 21855872 is about 279.5906944835.

The spelling of 21855872 in words is "twenty-one million, eight hundred fifty-five thousand, eight hundred seventy-two".