A number is prime if it doesn't have any divisors other than 1 and itself. Note that if such a divisor exists, one exists which is at most the square of the number. Given that N is less than 1000000, you only have to check less than 1000 numbers. And after testing 2, you can exclude all the other even numbers. Which leaves with at most 500 numbers to check.

Think you could write a program that checks the outcome of at most 500 divisions in less than a second?

In reply to Re: Find prime number between 1 to 1000000 by JavaFan
in thread Find prime number between 1 to 1000000 by mecrazycoder

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