81105191 has 4 divisors (see below), whose sum is σ = 81190032. Its totient is φ = 81020352.

The previous prime is 81105139. The next prime is 81105209. The reversal of 81105191 is 19150118.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81105191 - 2¹⁰ = 81104167 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81105191.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81105131) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 40970 + ... + 42903.

It is an arithmetic number, because the mean of its divisors is an integer number (20297508).

Almost surely, 2^81105191 is an apocalyptic number.

81105191 is a deficient number, since it is larger than the sum of its proper divisors (84841).

81105191 is an equidigital number, since it uses as much as digits as its factorization.

81105191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 84840.

The product of its (nonzero) digits is 360, while the sum is 26.

The square root of 81105191 is about 9005.8420483595. The cubic root of 81105191 is about 432.8620884357.

The spelling of 81105191 in words is "eighty-one million, one hundred five thousand, one hundred ninety-one".