79781 has 12 divisors (see below), whose sum is σ = 96012. Its totient is φ = 65664.

The previous prime is 79777. The next prime is 79801. The reversal of 79781 is 18797.

It can be written as a sum of positive squares in 2 ways, for example, as 36100 + 43681 = 190^2 + 209^2 .

It is not a de Polignac number, because 79781 - 2² = 79777 is a prime.

It is a super-2 number, since 2×79781² = 12730015922, which contains 22 as substring.

It is a Smith number, since the sum of its digits (32) coincides with the sum of the digits of its prime factors.

It is a Duffinian number.

Its product of digits (3528) is a multiple of the sum of its prime divisors (49).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (79181) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4190 + ... + 4208.

It is an arithmetic number, because the mean of its divisors is an integer number (8001).

2⁷⁹⁷⁸¹ is an apocalyptic number.

It is an amenable number.

79781 is a deficient number, since it is larger than the sum of its proper divisors (16231).

79781 is a wasteful number, since it uses less digits than its factorization.

79781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68 (or 49 counting only the distinct ones).

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

The square root of 79781 is about 282.4553061991. The cubic root of 79781 is about 43.0493394348.

It can be divided in two parts, 797 and 81, that added together give a palindrome (878).

The spelling of 79781 in words is "seventy-nine thousand, seven hundred eighty-one".