How To Find Prime Numbers

I know this probably isn't extremely interesting, or even worth reading about. But I thought is was a good question. It's one mathematicians are still trying to answer. The simplest method was developed by Eratosthenes in the 3rd century B.C. Here's how it works: Suppose we want to find all the prime numbers between 1 and 64. We write out a table of these numbers, 1-6 then start a new row and proceed as follows. The number 2 is the first integer greater than 1, so it is obviously prime. We now cross out all multiples of two. The next number that we haven't crossed out is 3. We circle it and cross out all its multiples. The next non-crossed-out number is 5, so we circle it and cross out all its multiples. We only have to do this for all numbers less than the square root of our upper limit (in this case sqrt(64)=8) since any composite number in the table must have at least one factor less than the square root of the upper limit. What's left after this process of elimination is all the prime numbers between 1 and 64. This is what it should look like!!





Unfortunately, this method is rather time consuming when the numbers you are looking for are much larger. But I thought it was neat. Try not to ban me from the blogging cirlce for this! :)

Here, let me give you something funny. I will in the future, be sharing some definitions of different fears: arachibutyrophobia=peanut butter sticking to the roof of the mouth!