81913 has 4 divisors (see below), whose sum is σ = 88228. Its totient is φ = 75600.

The previous prime is 81901. The next prime is 81919. The reversal of 81913 is 31918.

81913 is nontrivially palindromic in base 2.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 31918 = 2 ⋅15959.

It can be written as a sum of positive squares in 2 ways, for example, as 29929 + 51984 = 173^2 + 228^2 .

It is a cyclic number.

It is not a de Polignac number, because 81913 - 2⁹ = 81401 is a prime.

It is a Duffinian number.

81913 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (81919) 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, 3138 + ... + 3163.

It is an arithmetic number, because the mean of its divisors is an integer number (22057).

2⁸¹⁹¹³ is an apocalyptic number.

It is an amenable number.

81913 is a deficient number, since it is larger than the sum of its proper divisors (6315).

81913 is a wasteful number, since it uses less digits than its factorization.

81913 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6314.

The product of its digits is 216, while the sum is 22.

The square root of 81913 is about 286.2044723620. The cubic root of 81913 is about 43.4294447910.

The spelling of 81913 in words is "eighty-one thousand, nine hundred thirteen".