JavaFan,
And after testing 2, you can exclude all the other even numbers. Which leaves with at most 500 numbers to check.

After testing 3 and 5, you can use the 2/4 trick (see Re^3: a close prime number) to skip all multiples of 3 leaving you with about 333 numbers to check. I agree that for a single number under 1 million a pure perl function can be created that does the job without resorting to anything more advanced. I have yet to find a simple (by my own subjective definition) method though that does better than testing 1/3 sqrt (N) numbers to determine if a number is prime. I guess it could be argued that using Math::Pari's primality test function is simple but I meant my own implementation.

Cheers - L~R

In reply to Re^2: Find prime number between 1 to 1000000 by Limbic~Region
in thread Find prime number between 1 to 1000000 by mecrazycoder

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