81779 has 4 divisors (see below), whose sum is σ = 83376. Its totient is φ = 80184.

The previous prime is 81773. The next prime is 81799. The reversal of 81779 is 97718.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 97718 = 2 ⋅48859.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81779 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81773) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 719 + ... + 824.

It is an arithmetic number, because the mean of its divisors is an integer number (20844).

2⁸¹⁷⁷⁹ is an apocalyptic number.

81779 is a deficient number, since it is larger than the sum of its proper divisors (1597).

81779 is a wasteful number, since it uses less digits than its factorization.

81779 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1596.

The product of its digits is 3528, while the sum is 32.

The square root of 81779 is about 285.9702781759. The cubic root of 81779 is about 43.4057500504.

The spelling of 81779 in words is "eighty-one thousand, seven hundred seventy-nine".