81439 has 2 divisors, whose sum is σ = 81440. Its totient is φ = 81438.

The previous prime is 81421. The next prime is 81457. The reversal of 81439 is 93418.

It is a balanced prime because it is at equal distance from previous prime (81421) and next prime (81457).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81439 is a prime.

It is an Ulam number.

81439 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81409) 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, 40719 + 40720.

It is an arithmetic number, because the mean of its divisors is an integer number (40720).

2⁸¹⁴³⁹ is an apocalyptic number.

81439 is a deficient number, since it is larger than the sum of its proper divisors (1).

81439 is an equidigital number, since it uses as much as digits as its factorization.

81439 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 864, while the sum is 25.

The square root of 81439 is about 285.3751916338. The cubic root of 81439 is about 43.3455126844.

The spelling of 81439 in words is "eighty-one thousand, four hundred thirty-nine".