856243109 has 2 divisors, whose sum is σ = 856243110. Its totient is φ = 856243108.

The previous prime is 856243043. The next prime is 856243111. The reversal of 856243109 is 901342658.

It is a happy number.

856243109 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., 819676900 + 36566209 = 28630^2 + 6047^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-856243109 is a prime.

Together with 856243111, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (856243909) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 428121554 + 428121555.

It is an arithmetic number, because the mean of its divisors is an integer number (428121555).

Almost surely, 2^856243109 is an apocalyptic number.

It is an amenable number.

856243109 is a deficient number, since it is larger than the sum of its proper divisors (1).

856243109 is an equidigital number, since it uses as much as digits as its factorization.

856243109 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 51840, while the sum is 38.

The square root of 856243109 is about 29261.6320289898. The cubic root of 856243109 is about 949.5817582765.

The spelling of 856243109 in words is "eight hundred fifty-six million, two hundred forty-three thousand, one hundred nine".