391687913 has 2 divisors, whose sum is σ = 391687914. Its totient is φ = 391687912.

The previous prime is 391687847. The next prime is 391687931. The reversal of 391687913 is 319786193.

It is a happy number.

Together with next prime (391687931) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 315701824 + 75986089 = 17768^2 + 8717^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-391687913 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (391687943) 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, 195843956 + 195843957.

It is an arithmetic number, because the mean of its divisors is an integer number (195843957).

Almost surely, 2^391687913 is an apocalyptic number.

It is an amenable number.

391687913 is a deficient number, since it is larger than the sum of its proper divisors (1).

391687913 is an equidigital number, since it uses as much as digits as its factorization.

391687913 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 244944, while the sum is 47.

The square root of 391687913 is about 19791.1069169968. The cubic root of 391687913 is about 731.6668690547. Note that the first 3 decimals are identical.

The spelling of 391687913 in words is "three hundred ninety-one million, six hundred eighty-seven thousand, nine hundred thirteen".