840840391 has 2 divisors, whose sum is σ = 840840392. Its totient is φ = 840840390.

The previous prime is 840840367. The next prime is 840840439. The reversal of 840840391 is 193048048.

840840391 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 840840391 - 2⁵ = 840840359 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 840840391.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (840840331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 420420195 + 420420196.

It is an arithmetic number, because the mean of its divisors is an integer number (420420196).

Almost surely, 2^840840391 is an apocalyptic number.

840840391 is a deficient number, since it is larger than the sum of its proper divisors (1).

840840391 is an equidigital number, since it uses as much as digits as its factorization.

840840391 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 27648, while the sum is 37.

The square root of 840840391 is about 28997.2479901111. The cubic root of 840840391 is about 943.8533505166.

The spelling of 840840391 in words is "eight hundred forty million, eight hundred forty thousand, three hundred ninety-one".