991161212777 has 2 divisors, whose sum is σ = 991161212778. Its totient is φ = 991161212776.

The previous prime is 991161212753. The next prime is 991161212843. The reversal of 991161212777 is 777212161199.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 971839100761 + 19322112016 = 985819^2 + 139004^2 .

It is a cyclic number.

It is not a de Polignac number, because 991161212777 - 2²⁸ = 990892777321 is a prime.

It is not a weakly prime, because it can be changed into another prime (991161212747) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495580606388 + 495580606389.

It is an arithmetic number, because the mean of its divisors is an integer number (495580606389).

Almost surely, 2^991161212777 is an apocalyptic number.

It is an amenable number.

991161212777 is a deficient number, since it is larger than the sum of its proper divisors (1).

991161212777 is an equidigital number, since it uses as much as digits as its factorization.

991161212777 is an evil number, because the sum of its binary digits is even.

The product of its digits is 666792, while the sum is 53.

The spelling of 991161212777 in words is "nine hundred ninety-one billion, one hundred sixty-one million, two hundred twelve thousand, seven hundred seventy-seven".