81739239 has 4 divisors (see below), whose sum is σ = 108985656. Its totient is φ = 54492824.

The previous prime is 81739237. The next prime is 81739241. The reversal of 81739239 is 93293718.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (81739237) and next prime (81739241).

It is a cyclic number.

It is not a de Polignac number, because 81739239 - 2¹ = 81739237 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81739239.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81739237) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13623204 + ... + 13623209.

It is an arithmetic number, because the mean of its divisors is an integer number (27246414).

Almost surely, 2^81739239 is an apocalyptic number.

81739239 is a deficient number, since it is larger than the sum of its proper divisors (27246417).

81739239 is a wasteful number, since it uses less digits than its factorization.

81739239 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27246416.

The product of its digits is 81648, while the sum is 42.

The square root of 81739239 is about 9040.9755557683. The cubic root of 81739239 is about 433.9871427594.

The spelling of 81739239 in words is "eighty-one million, seven hundred thirty-nine thousand, two hundred thirty-nine".