81739757138 has 18 divisors (see below), whose sum is σ = 132775184997. Its totient is φ = 37723615800.

The previous prime is 81739757123. The next prime is 81739757233. The reversal of 81739757138 is 83175793718.

It can be written as a sum of positive squares in 2 ways, for example, as 69889910689 + 11849846449 = 264367^2 + 108857^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=202163.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 5248463 + ... + 5264013.

Almost surely, 2^81739757138 is an apocalyptic number.

81739757138 is a deficient number, since it is larger than the sum of its proper divisors (51035427859).

81739757138 is an frugal number, since it uses more digits than its factorization.

81739757138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31130 (or 15566 counting only the distinct ones).

The product of its digits is 8890560, while the sum is 59.

The spelling of 81739757138 in words is "eighty-one billion, seven hundred thirty-nine million, seven hundred fifty-seven thousand, one hundred thirty-eight".