81591078 has 32 divisors (see below), whose sum is σ = 167032800. Its totient is φ = 26562816.

The previous prime is 81591071. The next prime is 81591113. The reversal of 81591078 is 87019518.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81591071) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 46888 + ... + 48596.

It is an arithmetic number, because the mean of its divisors is an integer number (5219775).

Almost surely, 2^81591078 is an apocalyptic number.

81591078 is an abundant number, since it is smaller than the sum of its proper divisors (85441722).

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

81591078 is a wasteful number, since it uses less digits than its factorization.

81591078 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1896.

The product of its (nonzero) digits is 20160, while the sum is 39.

The square root of 81591078 is about 9032.7779780088. Note that the first 3 decimals coincide. The cubic root of 81591078 is about 433.7247683308.

The spelling of 81591078 in words is "eighty-one million, five hundred ninety-one thousand, seventy-eight".