991297920077 has 2 divisors, whose sum is σ = 991297920078. Its totient is φ = 991297920076.

The previous prime is 991297920061. The next prime is 991297920131. The reversal of 991297920077 is 770029792199.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 902688109801 + 88609810276 = 950099^2 + 297674^2 .

It is an emirp because it is prime and its reverse (770029792199) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 991297920077 - 2⁴ = 991297920061 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991297920047) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495648960038 + 495648960039.

It is an arithmetic number, because the mean of its divisors is an integer number (495648960039).

Almost surely, 2^991297920077 is an apocalyptic number.

It is an amenable number.

991297920077 is a deficient number, since it is larger than the sum of its proper divisors (1).

991297920077 is an equidigital number, since it uses as much as digits as its factorization.

991297920077 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9001692, while the sum is 62.

The spelling of 991297920077 in words is "nine hundred ninety-one billion, two hundred ninety-seven million, nine hundred twenty thousand, seventy-seven".