21855172 has 6 divisors (see below), whose sum is σ = 38246558. Its totient is φ = 10927584.

The previous prime is 21855161. The next prime is 21855191. The reversal of 21855172 is 27155812.

It can be written as a sum of positive squares in only one way, i.e., 15872256 + 5982916 = 3984^2 + 2446^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2731893 + ... + 2731900.

Almost surely, 2^21855172 is an apocalyptic number.

It is an amenable number.

21855172 is a deficient number, since it is larger than the sum of its proper divisors (16391386).

21855172 is a wasteful number, since it uses less digits than its factorization.

21855172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5463797 (or 5463795 counting only the distinct ones).

The product of its digits is 5600, while the sum is 31.

The square root of 21855172 is about 4674.9515505511. The cubic root of 21855172 is about 279.5877095408.

The spelling of 21855172 in words is "twenty-one million, eight hundred fifty-five thousand, one hundred seventy-two".