857811809 has 2 divisors, whose sum is σ = 857811810. Its totient is φ = 857811808.

The previous prime is 857811781. The next prime is 857811833. The reversal of 857811809 is 908118758.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 837813025 + 19998784 = 28945^2 + 4472^2 .

It is a cyclic number.

It is not a de Polignac number, because 857811809 - 2¹⁶ = 857746273 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (857817809) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 428905904 + 428905905.

It is an arithmetic number, because the mean of its divisors is an integer number (428905905).

Almost surely, 2^857811809 is an apocalyptic number.

It is an amenable number.

857811809 is a deficient number, since it is larger than the sum of its proper divisors (1).

857811809 is an equidigital number, since it uses as much as digits as its factorization.

857811809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 161280, while the sum is 47.

The square root of 857811809 is about 29288.4244881830. The cubic root of 857811809 is about 950.1613055735.

The spelling of 857811809 in words is "eight hundred fifty-seven million, eight hundred eleven thousand, eight hundred nine".