81729618073 has 2 divisors, whose sum is σ = 81729618074. Its totient is φ = 81729618072.

The previous prime is 81729618059. The next prime is 81729618077. The reversal of 81729618073 is 37081692718.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 66423721984 + 15305896089 = 257728^2 + 123717^2 .

It is a cyclic number.

It is not a de Polignac number, because 81729618073 - 2⁵ = 81729618041 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81729618073.

It is not a weakly prime, because it can be changed into another prime (81729618077) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40864809036 + 40864809037.

It is an arithmetic number, because the mean of its divisors is an integer number (40864809037).

Almost surely, 2^81729618073 is an apocalyptic number.

It is an amenable number.

81729618073 is a deficient number, since it is larger than the sum of its proper divisors (1).

81729618073 is an equidigital number, since it uses as much as digits as its factorization.

81729618073 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1016064, while the sum is 52.

The spelling of 81729618073 in words is "eighty-one billion, seven hundred twenty-nine million, six hundred eighteen thousand, seventy-three".