991475957 has 2 divisors, whose sum is σ = 991475958. Its totient is φ = 991475956.

The previous prime is 991475941. The next prime is 991475959. The reversal of 991475957 is 759574199.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 968827876 + 22648081 = 31126^2 + 4759^2 .

It is an emirp because it is prime and its reverse (759574199) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 991475957 - 2⁴ = 991475941 is a prime.

Together with 991475959, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991475959) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495737978 + 495737979.

It is an arithmetic number, because the mean of its divisors is an integer number (495737979).

Almost surely, 2^991475957 is an apocalyptic number.

It is an amenable number.

991475957 is a deficient number, since it is larger than the sum of its proper divisors (1).

991475957 is an equidigital number, since it uses as much as digits as its factorization.

991475957 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3572100, while the sum is 56.

The square root of 991475957 is about 31487.7112061198. The cubic root of 991475957 is about 997.1505406266.

The spelling of 991475957 in words is "nine hundred ninety-one million, four hundred seventy-five thousand, nine hundred fifty-seven".