81636 has 12 divisors (see below), whose sum is σ = 190512. Its totient is φ = 27208.

The previous prime is 81629. The next prime is 81637. The reversal of 81636 is 63618.

It is a tau number, because it is divible by the number of its divisors (12).

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors.

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

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 81636.

It is not an unprimeable number, because it can be changed into a prime (81637) by changing a digit.

81636 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, 3390 + ... + 3413.

It is an arithmetic number, because the mean of its divisors is an integer number (15876).

2⁸¹⁶³⁶ is an apocalyptic number.

It is an amenable number.

81636 is an abundant number, since it is smaller than the sum of its proper divisors (108876).

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 (95256).

81636 is a wasteful number, since it uses less digits than its factorization.

81636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6810 (or 6808 counting only the distinct ones).

The product of its digits is 864, while the sum is 24.

The square root of 81636 is about 285.7201427971. The cubic root of 81636 is about 43.3804353051.

It can be divided in two parts, 81 and 636, that added together give a palindrome (717).

The spelling of 81636 in words is "eighty-one thousand, six hundred thirty-six".