840239 has 2 divisors, whose sum is σ = 840240. Its totient is φ = 840238.

The previous prime is 840223. The next prime is 840241. The reversal of 840239 is 932048.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 840239 - 2⁴ = 840223 is a prime.

Together with 840241, it forms a pair of twin primes.

It is a Chen prime.

It is a plaindrome in base 13.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (840269) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 420119 + 420120.

It is an arithmetic number, because the mean of its divisors is an integer number (420120).

2⁸⁴⁰²³⁹ is an apocalyptic number.

840239 is a deficient number, since it is larger than the sum of its proper divisors (1).

840239 is an equidigital number, since it uses as much as digits as its factorization.

840239 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1728, while the sum is 26.

The square root of 840239 is about 916.6455149075. The cubic root of 840239 is about 94.3628273995.

Subtracting 840239 from its reverse (932048), we obtain a square (91809 = 303²).

The spelling of 840239 in words is "eight hundred forty thousand, two hundred thirty-nine".