991691317 has 4 divisors (see below), whose sum is σ = 993640140. Its totient is φ = 989742496.

The previous prime is 991691287. The next prime is 991691329. The reversal of 991691317 is 713196199.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 713196199 = 31 ⋅23006329.

It can be written as a sum of positive squares in 2 ways, for example, as 784504081 + 207187236 = 28009^2 + 14394^2 .

It is a cyclic number.

It is not a de Polignac number, because 991691317 - 2²³ = 983302709 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991691347) 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 in 3 ways as a sum of consecutive naturals, for example, 973648 + ... + 974665.

It is an arithmetic number, because the mean of its divisors is an integer number (248410035).

Almost surely, 2^991691317 is an apocalyptic number.

It is an amenable number.

991691317 is a deficient number, since it is larger than the sum of its proper divisors (1948823).

991691317 is a wasteful number, since it uses less digits than its factorization.

991691317 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1948822.

The product of its digits is 91854, while the sum is 46.

The square root of 991691317 is about 31491.1307672494. The cubic root of 991691317 is about 997.2227329282. Note that the first 3 decimals are identical.

The spelling of 991691317 in words is "nine hundred ninety-one million, six hundred ninety-one thousand, three hundred seventeen".