81985191 has 8 divisors (see below), whose sum is σ = 110853504. Its totient is φ = 53886840.

The previous prime is 81985187. The next prime is 81985207. The reversal of 81985191 is 19158918.

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

It is not a de Polignac number, because 81985191 - 2² = 81985187 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 congruent number.

It is not an unprimeable number, because it can be changed into a prime (81985121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 192241 + ... + 192666.

It is an arithmetic number, because the mean of its divisors is an integer number (13856688).

Almost surely, 2^81985191 is an apocalyptic number.

81985191 is a deficient number, since it is larger than the sum of its proper divisors (28868313).

81985191 is a wasteful number, since it uses less digits than its factorization.

81985191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 384981.

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

The square root of 81985191 is about 9054.5674109810. The cubic root of 81985191 is about 434.4219935770.

The spelling of 81985191 in words is "eighty-one million, nine hundred eighty-five thousand, one hundred ninety-one".