Prime Number Detector

Input a number to determine if it is prime.

The maximum input value before truncation error is 9007199254740991 (~9e15, nine and fifteen zeros!), which is not prime but has a relatively large least factor. This is because JavaScript uses double-precision floating-point numbers according to IEEE 754, and this number is the largest this format supports.

Notes

I used this little project to get my feet wet with Javascript when I was building my website from raw HTML and CSS. I also enjoyed implementing some tricks to accelerate the solution, the main one being the square root bound on the factors.