81766 has 4 divisors (see below), whose sum is σ = 122652. Its totient is φ = 40882.

The previous prime is 81761. The next prime is 81769. The reversal of 81766 is 66718.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 66718 = 2 ⋅33359.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81761) by changing a digit.

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 as a sum of consecutive naturals, namely, 20440 + ... + 20443.

It is an arithmetic number, because the mean of its divisors is an integer number (30663).

2⁸¹⁷⁶⁶ is an apocalyptic number.

81766 is a deficient number, since it is larger than the sum of its proper divisors (40886).

81766 is a wasteful number, since it uses less digits than its factorization.

81766 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40885.

The product of its digits is 2016, while the sum is 28.

The square root of 81766 is about 285.9475476377. The cubic root of 81766 is about 43.4034499300.

The spelling of 81766 in words is "eighty-one thousand, seven hundred sixty-six".