Q: Is 666,561 a Prime Number?
A: No, 666,561 is not a prime number.
A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 666561 can be evenly divided by 1 3 7 21 31,741 95,223 222,187 and 666,561, with no remainder.
Since 666,561 cannot be divided by just 1 and 666,561, it is not a prime number.