191171821817 has 2 divisors, whose sum is σ = 191171821818. Its totient is φ = 191171821816.

The previous prime is 191171821807. The next prime is 191171821849. The reversal of 191171821817 is 718128171191.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 150256241641 + 40915580176 = 387629^2 + 202276^2 .

It is a cyclic number.

It is not a de Polignac number, because 191171821817 - 2¹⁰ = 191171820793 is a prime.

It is not a weakly prime, because it can be changed into another prime (191171821807) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95585910908 + 95585910909.

It is an arithmetic number, because the mean of its divisors is an integer number (95585910909).

Almost surely, 2^191171821817 is an apocalyptic number.

It is an amenable number.

191171821817 is a deficient number, since it is larger than the sum of its proper divisors (1).

191171821817 is an equidigital number, since it uses as much as digits as its factorization.

191171821817 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 56448, while the sum is 47.

The spelling of 191171821817 in words is "one hundred ninety-one billion, one hundred seventy-one million, eight hundred twenty-one thousand, eight hundred seventeen".