666857 has 2 divisors, whose sum is σ = 666858. Its totient is φ = 666856.

The previous prime is 666829. The next prime is 666871. The reversal of 666857 is 758666.

666857 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., 534361 + 132496 = 731^2 + 364^2 .

It is a cyclic number.

It is not a de Polignac number, because 666857 - 2¹⁸ = 404713 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 666857.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333428 + 333429.

It is an arithmetic number, because the mean of its divisors is an integer number (333429).

2⁶⁶⁶⁸⁵⁷ is an apocalyptic number.

It is an amenable number.

666857 is a deficient number, since it is larger than the sum of its proper divisors (1).

666857 is an equidigital number, since it uses as much as digits as its factorization.

666857 is an evil number, because the sum of its binary digits is even.

The product of its digits is 60480, while the sum is 38.

The square root of 666857 is about 816.6131274967. The cubic root of 666857 is about 87.3663592567.

Subtracting 666857 from its reverse (758666), we obtain a square (91809 = 303²).

The spelling of 666857 in words is "six hundred sixty-six thousand, eight hundred fifty-seven".