391998493 has 2 divisors, whose sum is σ = 391998494. Its totient is φ = 391998492.

The previous prime is 391998491. The next prime is 391998517. The reversal of 391998493 is 394899193.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 391921209 + 77284 = 19797^2 + 278^2 .

It is a cyclic number.

It is not a de Polignac number, because 391998493 - 2¹ = 391998491 is a prime.

Together with 391998491, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (391998491) 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, 195999246 + 195999247.

It is an arithmetic number, because the mean of its divisors is an integer number (195999247).

Almost surely, 2^391998493 is an apocalyptic number.

It is an amenable number.

391998493 is a deficient number, since it is larger than the sum of its proper divisors (1).

391998493 is an equidigital number, since it uses as much as digits as its factorization.

391998493 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1889568, while the sum is 55.

The square root of 391998493 is about 19798.9518156896. The cubic root of 391998493 is about 731.8602041507.

The spelling of 391998493 in words is "three hundred ninety-one million, nine hundred ninety-eight thousand, four hundred ninety-three".