856561129 has 2 divisors, whose sum is σ = 856561130. Its totient is φ = 856561128.

The previous prime is 856561087. The next prime is 856561141. The reversal of 856561129 is 921165658.

856561129 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., 494039529 + 362521600 = 22227^2 + 19040^2 .

It is a cyclic number.

It is not a de Polignac number, because 856561129 - 2²⁵ = 823006697 is a prime.

It is not a weakly prime, because it can be changed into another prime (856561159) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 428280564 + 428280565.

It is an arithmetic number, because the mean of its divisors is an integer number (428280565).

Almost surely, 2^856561129 is an apocalyptic number.

It is an amenable number.

856561129 is a deficient number, since it is larger than the sum of its proper divisors (1).

856561129 is an equidigital number, since it uses as much as digits as its factorization.

856561129 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 129600, while the sum is 43.

The square root of 856561129 is about 29267.0656028239. The cubic root of 856561129 is about 949.6993061272.

The spelling of 856561129 in words is "eight hundred fifty-six million, five hundred sixty-one thousand, one hundred twenty-nine".