391998491 has 2 divisors, whose sum is σ = 391998492. Its totient is φ = 391998490.

The previous prime is 391998433. The next prime is 391998493. The reversal of 391998491 is 194899193.

It is a strong prime.

It is an emirp because it is prime and its reverse (194899193) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-391998491 is a prime.

Together with 391998493, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (391998493) 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, 195999245 + 195999246.

It is an arithmetic number, because the mean of its divisors is an integer number (195999246).

Almost surely, 2^391998491 is an apocalyptic number.

391998491 is a deficient number, since it is larger than the sum of its proper divisors (1).

391998491 is an equidigital number, since it uses as much as digits as its factorization.

391998491 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 629856, while the sum is 53.

The square root of 391998491 is about 19798.9517651819. The cubic root of 391998491 is about 731.8602029061.

The spelling of 391998491 in words is "three hundred ninety-one million, nine hundred ninety-eight thousand, four hundred ninety-one".