81939 has 16 divisors (see below), whose sum is σ = 129024. Its totient is φ = 45600.

The previous prime is 81937. The next prime is 81943. The reversal of 81939 is 93918.

It is a happy number.

It is not a de Polignac number, because 81939 - 2¹ = 81937 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 334 + ... + 524.

It is an arithmetic number, because the mean of its divisors is an integer number (8064).

2⁸¹⁹³⁹ is an apocalyptic number.

81939 is a deficient number, since it is larger than the sum of its proper divisors (47085).

81939 is a wasteful number, since it uses less digits than its factorization.

81939 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 218.

The product of its digits is 1944, while the sum is 30.

The square root of 81939 is about 286.2498908297. The cubic root of 81939 is about 43.4340392840.

It can be divided in two parts, 8193 and 9, that multiplied together give a palindrome (73737).

The spelling of 81939 in words is "eighty-one thousand, nine hundred thirty-nine".