81399435917 has 2 divisors, whose sum is σ = 81399435918. Its totient is φ = 81399435916.

The previous prime is 81399435881. The next prime is 81399435937. The reversal of 81399435917 is 71953499318.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 81141801316 + 257634601 = 284854^2 + 16051^2 .

It is a cyclic number.

It is not a de Polignac number, because 81399435917 - 2⁸ = 81399435661 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81399435937) 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 as a sum of consecutive naturals, namely, 40699717958 + 40699717959.

It is an arithmetic number, because the mean of its divisors is an integer number (40699717959).

Almost surely, 2^81399435917 is an apocalyptic number.

It is an amenable number.

81399435917 is a deficient number, since it is larger than the sum of its proper divisors (1).

81399435917 is an equidigital number, since it uses as much as digits as its factorization.

81399435917 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7348320, while the sum is 59.

The spelling of 81399435917 in words is "eighty-one billion, three hundred ninety-nine million, four hundred thirty-five thousand, nine hundred seventeen".