391831081 has 2 divisors, whose sum is σ = 391831082. Its totient is φ = 391831080.

The previous prime is 391831061. The next prime is 391831117. The reversal of 391831081 is 180138193.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 380835225 + 10995856 = 19515^2 + 3316^2 .

It is an emirp because it is prime and its reverse (180138193) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 391831081 - 2¹³ = 391822889 is a prime.

It is a super-2 number, since 2×391831081² = 307063192075257122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (391831001) 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, 195915540 + 195915541.

It is an arithmetic number, because the mean of its divisors is an integer number (195915541).

Almost surely, 2^391831081 is an apocalyptic number.

It is an amenable number.

391831081 is a deficient number, since it is larger than the sum of its proper divisors (1).

391831081 is an equidigital number, since it uses as much as digits as its factorization.

391831081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5184, while the sum is 34.

The square root of 391831081 is about 19794.7235646270. The cubic root of 391831081 is about 731.7560033874.

The spelling of 391831081 in words is "three hundred ninety-one million, eight hundred thirty-one thousand, eighty-one".