81729617917 has 2 divisors, whose sum is σ = 81729617918. Its totient is φ = 81729617916.

The previous prime is 81729617873. The next prime is 81729617933. The reversal of 81729617917 is 71971692718.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 80409676356 + 1319941561 = 283566^2 + 36331^2 .

It is a cyclic number.

It is not a de Polignac number, because 81729617917 - 2¹⁹ = 81729093629 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81729617017) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40864808958 + 40864808959.

It is an arithmetic number, because the mean of its divisors is an integer number (40864808959).

Almost surely, 2^81729617917 is an apocalyptic number.

It is an amenable number.

81729617917 is a deficient number, since it is larger than the sum of its proper divisors (1).

81729617917 is an equidigital number, since it uses as much as digits as its factorization.

81729617917 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2667168, while the sum is 58.

The spelling of 81729617917 in words is "eighty-one billion, seven hundred twenty-nine million, six hundred seventeen thousand, nine hundred seventeen".