1991173965149 has 2 divisors, whose sum is σ = 1991173965150. Its totient is φ = 1991173965148.

The previous prime is 1991173965113. The next prime is 1991173965217. The reversal of 1991173965149 is 9415693711991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1460544760900 + 530629204249 = 1208530^2 + 728443^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1991173965149 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1991173365149) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995586982574 + 995586982575.

It is an arithmetic number, because the mean of its divisors is an integer number (995586982575).

Almost surely, 2^{1991173965149} is an apocalyptic number.

It is an amenable number.

1991173965149 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991173965149 is an equidigital number, since it uses as much as digits as its factorization.

1991173965149 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 16533720, while the sum is 65.

The spelling of 1991173965149 in words is "one trillion, nine hundred ninety-one billion, one hundred seventy-three million, nine hundred sixty-five thousand, one hundred forty-nine".