81812 has 12 divisors (see below), whose sum is σ = 145236. Its totient is φ = 40320.

The previous prime is 81799. The next prime is 81817. The reversal of 81812 is 21818.

It can be written as a sum of positive squares in 2 ways, for example, as 1156 + 80656 = 34^2 + 284^2 .

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81817) by changing a digit.

81812 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 3 ways as a sum of consecutive naturals, for example, 362 + ... + 542.

It is an arithmetic number, because the mean of its divisors is an integer number (12103).

2⁸¹⁸¹² is an apocalyptic number.

It is an amenable number.

81812 is a deficient number, since it is larger than the sum of its proper divisors (63424).

81812 is a wasteful number, since it uses less digits than its factorization.

81812 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 298 (or 296 counting only the distinct ones).

The product of its digits is 128, while the sum is 20.

The square root of 81812 is about 286.0279706602. The cubic root of 81812 is about 43.4115877232.

The spelling of 81812 in words is "eighty-one thousand, eight hundred twelve".