81171978 has 16 divisors (see below), whose sum is σ = 162719040. Its totient is φ = 26994816.

The previous prime is 81171977. The next prime is 81171989. The reversal of 81171978 is 87917118.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (81171977) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12775 + ... + 18042.

It is an arithmetic number, because the mean of its divisors is an integer number (10169940).

Almost surely, 2^81171978 is an apocalyptic number.

81171978 is an abundant number, since it is smaller than the sum of its proper divisors (81547062).

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

81171978 is a wasteful number, since it uses less digits than its factorization.

81171978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31261.

The product of its digits is 28224, while the sum is 42.

The square root of 81171978 is about 9009.5492673052. The cubic root of 81171978 is about 432.9808709216.

The spelling of 81171978 in words is "eighty-one million, one hundred seventy-one thousand, nine hundred seventy-eight".