81366 has 16 divisors (see below), whose sum is σ = 165888. Its totient is φ = 26600.

The previous prime is 81359. The next prime is 81371. The reversal of 81366 is 66318.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 331 + ... + 521.

It is an arithmetic number, because the mean of its divisors is an integer number (10368).

2⁸¹³⁶⁶ is an apocalyptic number.

81366 is an abundant number, since it is smaller than the sum of its proper divisors (84522).

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 (82944).

81366 is a wasteful number, since it uses less digits than its factorization.

81366 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 267.

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

The square root of 81366 is about 285.2472611613. The cubic root of 81366 is about 43.3325575141.

It can be divided in two parts, 81 and 366, that multiplied together give a triangular number (29646 = T₂₄₃).

The spelling of 81366 in words is "eighty-one thousand, three hundred sixty-six".