Is the number 999997 a prime number?

Easiest way to answer this question yourself is can this number be divided by 2 or 3 and not have a decimal or any "leftover" numbers?

999997 / 2 = 499998.5 = Nope

999997 / 3 = 333332.33 = Nope

Answer: Yes, 999997 is a Prime number.

No, the above is not a legitimate prime test. 999997 is actually 757 * 1321 and is not prime. There is no easy prime test you can do in your head that I know of.