81979 has 4 divisors (see below), whose sum is σ = 83176.
Its totient is φ = 80784.
The previous prime is 81973. The next prime is 82003. The reversal of 81979 is 97918.
It can be divided in two parts, 819 and 79, that added together give a palindrome (898).
It is a semiprime because it is the product of two primes.
It is a cyclic number.
It is not a de Polignac number, because 81979 - 23 = 81971 is a prime.
It is an Ulam number.
It is a Duffinian number.
It is not an unprimeable number, because it can be changed into a prime (81971) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (7) of ones.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 489 + ... + 634.
It is an arithmetic number, because the mean of its divisors is an integer number (20794).
281979 is an apocalyptic number.
81979 is a deficient number, since it is larger than the sum of its proper divisors (1197).
81979 is a wasteful number, since it uses less digits than its factorization.
81979 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 1196.
The product of its digits is 4536, while the sum is 34.
The square root of 81979 is about 286.3197513271.
The cubic root of 81979 is about 43.4411058373.
The spelling of 81979 in words is "eighty-one thousand, nine hundred seventy-nine".