81556172 has 12 divisors (see below), whose sum is σ = 145142760. Its totient is φ = 40086816.

The previous prime is 81556169. The next prime is 81556201. The reversal of 81556172 is 27165518.

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, 172553 + ... + 173024.

It is an arithmetic number, because the mean of its divisors is an integer number (12095230).

Almost surely, 2^81556172 is an apocalyptic number.

It is an amenable number.

81556172 is a deficient number, since it is larger than the sum of its proper divisors (63586588).

81556172 is a wasteful number, since it uses less digits than its factorization.

81556172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 345640 (or 345638 counting only the distinct ones).

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

The square root of 81556172 is about 9030.8455861010. The cubic root of 81556172 is about 433.6629079876.

The spelling of 81556172 in words is "eighty-one million, five hundred fifty-six thousand, one hundred seventy-two".