991878317 has 2 divisors, whose sum is σ = 991878318. Its totient is φ = 991878316.

The previous prime is 991878301. The next prime is 991878331. The reversal of 991878317 is 713878199.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 985583236 + 6295081 = 31394^2 + 2509^2 .

It is a cyclic number.

It is not a de Polignac number, because 991878317 - 2⁴ = 991878301 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991878367) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495939158 + 495939159.

It is an arithmetic number, because the mean of its divisors is an integer number (495939159).

Almost surely, 2^991878317 is an apocalyptic number.

It is an amenable number.

991878317 is a deficient number, since it is larger than the sum of its proper divisors (1).

991878317 is an equidigital number, since it uses as much as digits as its factorization.

991878317 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 762048, while the sum is 53.

The square root of 991878317 is about 31494.0997172486. The cubic root of 991878317 is about 997.2854100024.

The spelling of 991878317 in words is "nine hundred ninety-one million, eight hundred seventy-eight thousand, three hundred seventeen".