Prime Numbers

Prime Numbers

Prime numbers are whole number that can only be made by multiplying the given number by one and itself. So for example 3 would be a prime number because the only two numbers that you can multiply together to get 3 are (3 x 1). So 4 would not be a prime number because to get 4 you can multiply (2 x 2) as well as (4 x 1). Also the numbers that you can break bigger numbers into are called the numbers factors. So 1,2,4 would be factors of 4. 

Composite Numbers

Composite numbers are basically all the rest of the numbers that are not prime numbers. One thing to note is that 0 and 1 are not categorized as prime or composite numbers. So if a number is not prime and it’s not 0 or 1 then that number is known as a composite number. 

Tips On Finding Prime Number

All even numbers after 2 are composite numbers because they can always be divided by 2. So 6 is not a prime number because you can get six through the following (6 x 1) (3 x 2).

All numbers after 5 ending in 5 are composite numbers because they can be divided by 5. So you know that 35 is a composite number because 5 x 7 = 35.

One way to test if a number is prime is to start dividing it by all the lower prime numbers. This is an excellent way for smaller numbers and it is always worth it to at least try the prime number between 1 and 12. Example:

Is 13 a prime number?

So 13/2, 13/3, 13/5, 13/7, 13/11

Since none of these divide out evenly 13 must also be a prime number.

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