840839 has 2 divisors, whose sum is σ = 840840. Its totient is φ = 840838.

The previous prime is 840823. The next prime is 840841. The reversal of 840839 is 938048.

840839 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 840839 - 2⁴ = 840823 is a prime.

It is a Sophie Germain prime.

Together with 840841, it forms a pair of twin primes.

It is a Chen prime.

It is equal to p₆₆₉₄₇ and since 840839 and 66947 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (840859) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 420419 + 420420.

It is an arithmetic number, because the mean of its divisors is an integer number (420420).

2⁸⁴⁰⁸³⁹ is an apocalyptic number.

840839 is a deficient number, since it is larger than the sum of its proper divisors (1).

840839 is an equidigital number, since it uses as much as digits as its factorization.

840839 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6912, while the sum is 32.

The square root of 840839 is about 916.9727367812. The cubic root of 840839 is about 94.3852830045.

The spelling of 840839 in words is "eight hundred forty thousand, eight hundred thirty-nine".