81845 has 4 divisors (see below), whose sum is σ = 98220. Its totient is φ = 65472.

The previous prime is 81839. The next prime is 81847. The reversal of 81845 is 54818.

81845 is an esthetic number in base 11, because in such base its adjacent digits differ by 1.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 54818 = 2 ⋅27409.

It can be written as a sum of positive squares in 2 ways, for example, as 27556 + 54289 = 166^2 + 233^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81845 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81847) 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, 8180 + ... + 8189.

It is an arithmetic number, because the mean of its divisors is an integer number (24555).

2⁸¹⁸⁴⁵ is an apocalyptic number.

It is an amenable number.

81845 is a deficient number, since it is larger than the sum of its proper divisors (16375).

81845 is a wasteful number, since it uses less digits than its factorization.

81845 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16374.

The product of its digits is 1280, while the sum is 26.

The square root of 81845 is about 286.0856515102. The cubic root of 81845 is about 43.4174238264.

The spelling of 81845 in words is "eighty-one thousand, eight hundred forty-five".