81606 has 32 divisors (see below), whose sum is σ = 195840. Its totient is φ = 22176.

The previous prime is 81569. The next prime is 81611. The reversal of 81606 is 60618.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is an unprimeable number.

81606 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, 1185 + ... + 1251.

It is an arithmetic number, because the mean of its divisors is an integer number (6120).

2⁸¹⁶⁰⁶ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81606, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (97920).

81606 is an abundant number, since it is smaller than the sum of its proper divisors (114234).

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

81606 is a wasteful number, since it uses less digits than its factorization.

81606 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 108.

The product of its (nonzero) digits is 288, while the sum is 21.

The square root of 81606 is about 285.6676390493. The cubic root of 81606 is about 43.3751207686.

Subtracting from 81606 its product of nonzero digits (288), we obtain a palindrome (81318).

The spelling of 81606 in words is "eighty-one thousand, six hundred six".