81599957539 has 4 divisors (see below), whose sum is σ = 81601544880. Its totient is φ = 81598370200.

The previous prime is 81599957519. The next prime is 81599957557. The reversal of 81599957539 is 93575999518.

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 81599957539 - 2²³ = 81591568931 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81599957519) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 713887 + ... + 820264.

It is an arithmetic number, because the mean of its divisors is an integer number (20400386220).

Almost surely, 2^81599957539 is an apocalyptic number.

81599957539 is a deficient number, since it is larger than the sum of its proper divisors (1587341).

81599957539 is a wasteful number, since it uses less digits than its factorization.

81599957539 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1587340.

The product of its digits is 137781000, while the sum is 70.

The spelling of 81599957539 in words is "eighty-one billion, five hundred ninety-nine million, nine hundred fifty-seven thousand, five hundred thirty-nine".