81091 has 4 divisors (see below), whose sum is σ = 82152. Its totient is φ = 80032.

The previous prime is 81083. The next prime is 81097. The reversal of 81091 is 19018.

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 81091 - 2³ = 81083 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81097) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 406 + ... + 571.

It is an arithmetic number, because the mean of its divisors is an integer number (20538).

2⁸¹⁰⁹¹ is an apocalyptic number.

81091 is a deficient number, since it is larger than the sum of its proper divisors (1061).

81091 is an equidigital number, since it uses as much as digits as its factorization.

81091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1060.

The product of its (nonzero) digits is 72, while the sum is 19.

The square root of 81091 is about 284.7648152423. The cubic root of 81091 is about 43.2836840959.

The spelling of 81091 in words is "eighty-one thousand, ninety-one".