19817107957891 has 2 divisors, whose sum is σ = 19817107957892. Its totient is φ = 19817107957890.

The previous prime is 19817107957877. The next prime is 19817107957909. The reversal of 19817107957891 is 19875970171891.

It is a weak prime.

It is an emirp because it is prime and its reverse (19875970171891) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19817107957891 - 2²⁹ = 19816571086979 is a prime.

It is not a weakly prime, because it can be changed into another prime (19817107957831) 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, 9908553978945 + 9908553978946.

It is an arithmetic number, because the mean of its divisors is an integer number (9908553978946).

Almost surely, 2^{19817107957891} is an apocalyptic number.

19817107957891 is a deficient number, since it is larger than the sum of its proper divisors (1).

19817107957891 is an equidigital number, since it uses as much as digits as its factorization.

19817107957891 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 80015040, while the sum is 73.

The spelling of 19817107957891 in words is "nineteen trillion, eight hundred seventeen billion, one hundred seven million, nine hundred fifty-seven thousand, eight hundred ninety-one".