391649873 has 2 divisors, whose sum is σ = 391649874. Its totient is φ = 391649872.

The previous prime is 391649861. The next prime is 391649879. The reversal of 391649873 is 378946193.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 367757329 + 23892544 = 19177^2 + 4888^2 .

It is a cyclic number.

It is not a de Polignac number, because 391649873 - 2¹⁸ = 391387729 is a prime.

It is a super-2 number, since 2×391649873² = 306779246041832258, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (391649879) 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 as a sum of consecutive naturals, namely, 195824936 + 195824937.

It is an arithmetic number, because the mean of its divisors is an integer number (195824937).

Almost surely, 2^391649873 is an apocalyptic number.

It is an amenable number.

391649873 is a deficient number, since it is larger than the sum of its proper divisors (1).

391649873 is an equidigital number, since it uses as much as digits as its factorization.

391649873 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 979776, while the sum is 50.

The square root of 391649873 is about 19790.1458559557. The cubic root of 391649873 is about 731.6431822471.

The spelling of 391649873 in words is "three hundred ninety-one million, six hundred forty-nine thousand, eight hundred seventy-three".