81816 has 32 divisors (see below), whose sum is σ = 234240. Its totient is φ = 23328.

The previous prime is 81799. The next prime is 81817. The reversal of 81816 is 61818.

81816 = T₁₃₉ + T₁₄₀ + ... + T₁₄₆.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a nude number because it is divisible by every one of its digits.

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.

81816 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 7 ways as a sum of consecutive naturals, for example, 76 + ... + 411.

It is an arithmetic number, because the mean of its divisors is an integer number (7320).

2⁸¹⁸¹⁶ is an apocalyptic number.

It is an amenable number.

81816 is an abundant number, since it is smaller than the sum of its proper divisors (152424).

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

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (117120).

81816 is a wasteful number, since it uses less digits than its factorization.

81816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 503 (or 499 counting only the distinct ones).

The product of its digits is 384, while the sum is 24.

The square root of 81816 is about 286.0349628979. The cubic root of 81816 is about 43.4122952132.

The spelling of 81816 in words is "eighty-one thousand, eight hundred sixteen".