840878309 has 2 divisors, whose sum is σ = 840878310. Its totient is φ = 840878308.

The previous prime is 840878267. The next prime is 840878329. The reversal of 840878309 is 903878048.

840878309 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 can be written as a sum of positive squares in only one way, i.e., 812820100 + 28058209 = 28510^2 + 5297^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-840878309 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (840878329) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 420439154 + 420439155.

It is an arithmetic number, because the mean of its divisors is an integer number (420439155).

Almost surely, 2^840878309 is an apocalyptic number.

It is an amenable number.

840878309 is a deficient number, since it is larger than the sum of its proper divisors (1).

840878309 is an equidigital number, since it uses as much as digits as its factorization.

840878309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 387072, while the sum is 47.

The square root of 840878309 is about 28997.9018034064. The cubic root of 840878309 is about 943.8675381055.

The spelling of 840878309 in words is "eight hundred forty million, eight hundred seventy-eight thousand, three hundred nine".