81172911986 has 8 divisors (see below), whose sum is σ = 121767249324. Its totient is φ = 40583828880.

The previous prime is 81172911979. The next prime is 81172911991. The reversal of 81172911986 is 68911927118.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 80420452225 + 752459761 = 283585^2 + 27431^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

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, 1274705 + ... + 1336868.

Almost surely, 2^81172911986 is an apocalyptic number.

81172911986 is a deficient number, since it is larger than the sum of its proper divisors (40594337338).

81172911986 is a wasteful number, since it uses less digits than its factorization.

81172911986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2627116.

The product of its digits is 435456, while the sum is 53.

The spelling of 81172911986 in words is "eighty-one billion, one hundred seventy-two million, nine hundred eleven thousand, nine hundred eighty-six".