81791 has 4 divisors (see below), whose sum is σ = 82800. Its totient is φ = 80784.

The previous prime is 81773. The next prime is 81799. The reversal of 81791 is 19718.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19718 = 2 ⋅9859.

It is a cyclic number.

It is not a de Polignac number, because 81791 - 2⁶ = 81727 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 81791.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81799) 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, 371 + ... + 548.

It is an arithmetic number, because the mean of its divisors is an integer number (20700).

2⁸¹⁷⁹¹ is an apocalyptic number.

81791 is a deficient number, since it is larger than the sum of its proper divisors (1009).

81791 is an equidigital number, since it uses as much as digits as its factorization.

81791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1008.

The product of its digits is 504, while the sum is 26.

The square root of 81791 is about 285.9912586077. The cubic root of 81791 is about 43.4078730222.

It can be divided in two parts, 817 and 91, that multiplied together give a palindrome (74347).

The spelling of 81791 in words is "eighty-one thousand, seven hundred ninety-one".