81181986 has 24 divisors (see below), whose sum is σ = 164683440. Its totient is φ = 26679456.

The previous prime is 81181951. The next prime is 81181993. The reversal of 81181986 is 68918118.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 30705 + ... + 33243.

It is an arithmetic number, because the mean of its divisors is an integer number (6861810).

Almost surely, 2^81181986 is an apocalyptic number.

81181986 is an abundant number, since it is smaller than the sum of its proper divisors (83501454).

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

81181986 is a wasteful number, since it uses less digits than its factorization.

81181986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2690 (or 2617 counting only the distinct ones).

The product of its digits is 27648, while the sum is 42.

The square root of 81181986 is about 9010.1046608794. The cubic root of 81181986 is about 432.9986648064.

The spelling of 81181986 in words is "eighty-one million, one hundred eighty-one thousand, nine hundred eighty-six".