81181959 has 8 divisors (see below), whose sum is σ = 111168240. Its totient is φ = 52658496.

The previous prime is 81181951. The next prime is 81181993. The reversal of 81181959 is 95918118.

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

It is not a de Polignac number, because 81181959 - 2³ = 81181951 is a prime.

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 81181959.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81181951) 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, 365574 + ... + 365795.

It is an arithmetic number, because the mean of its divisors is an integer number (13896030).

Almost surely, 2^81181959 is an apocalyptic number.

81181959 is a deficient number, since it is larger than the sum of its proper divisors (29986281).

81181959 is a wasteful number, since it uses less digits than its factorization.

81181959 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 731409.

The product of its digits is 25920, while the sum is 42.

The square root of 81181959 is about 9010.1031625615. The cubic root of 81181959 is about 432.9986168033.

The spelling of 81181959 in words is "eighty-one million, one hundred eighty-one thousand, nine hundred fifty-nine".