81918 has 32 divisors (see below), whose sum is σ = 191520. Its totient is φ = 25920.

The previous prime is 81901. The next prime is 81919.

81918 is nontrivially palindromic in base 10.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an Ulam number.

It is a junction number, because it is equal to n+sod(n) for n = 81891 and 81900.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81919) by changing a digit.

81918 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1978 + ... + 2018.

It is an arithmetic number, because the mean of its divisors is an integer number (5985).

2⁸¹⁹¹⁸ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81918, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (95760).

81918 is an abundant number, since it is smaller than the sum of its proper divisors (109602).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81918 is a wasteful number, since it uses less digits than its factorization.

81918 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89 (or 83 counting only the distinct ones).

The product of its digits is 576, while the sum is 27.

The square root of 81918 is about 286.2132072424. The cubic root of 81918 is about 43.4303284228.

It can be divided in two parts, 81 and 918, that added together give a palindrome (999).

The spelling of 81918 in words is "eighty-one thousand, nine hundred eighteen".