991365257 has 2 divisors, whose sum is σ = 991365258. Its totient is φ = 991365256.

The previous prime is 991365241. The next prime is 991365311. The reversal of 991365257 is 752563199.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 560221561 + 431143696 = 23669^2 + 20764^2 .

It is an emirp because it is prime and its reverse (752563199) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 991365257 - 2⁴ = 991365241 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (991365227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495682628 + 495682629.

It is an arithmetic number, because the mean of its divisors is an integer number (495682629).

Almost surely, 2^991365257 is an apocalyptic number.

It is an amenable number.

991365257 is a deficient number, since it is larger than the sum of its proper divisors (1).

991365257 is an equidigital number, since it uses as much as digits as its factorization.

991365257 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 510300, while the sum is 47.

The square root of 991365257 is about 31485.9533284289. The cubic root of 991365257 is about 997.1134280530.

The spelling of 991365257 in words is "nine hundred ninety-one million, three hundred sixty-five thousand, two hundred fifty-seven".