# Identifying Prime & Composite Numbers

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• 0:01 Numbers
• 0:37 Prime Numbers
• 1:52 Composite Numbers
• 3:16 Example
• 4:17 Lesson Summary
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Lesson Transcript
Instructor: Yuanxin (Amy) Yang Alcocer

Amy has a master's degree in secondary education and has taught math at a public charter high school.

In this video lesson, you will learn how to identify both prime and composite numbers. You will also learn what makes the numbers unique, as well as the characteristics of both these types of numbers.

## Numbers

Our world runs on numbers. Without numbers, we wouldn't have money or business or anything. Just a visit to the store and you are bombarded with numbers left and right. You can't purchase any candy or gum or donuts or fries without coming across numbers. And, of course, we wouldn't have our wonderful math classes and lessons without numbers! In this video lesson, we'll look at two different types of numbers. You will learn what makes them unique and how to identify them. The two types of numbers that we will look at are prime numbers and composite numbers.

## Prime Numbers

We begin with prime numbers. A prime number is a number that is divisible by only 1 and itself. All prime numbers are positive. For example, 1 is a prime number because 1 can only be divided by 1 and itself, 1. 2 is also a prime number because it can only be divided by 1 and itself, 2. 3 is also a prime number because it can only be divided by 1 and itself, 3.

Another way you can identify prime numbers is if you try to divide the number into equal groups (groups that all contain the same number of items) where each group has more than 1. For example, say you had 3 candies. If you want to divide these 3 candies into equal groups, the only way you can do this is if you divided it into 3 equal groups where each group has only 1 candy.

It is impossible to divide a prime number into equal groups where each group has more than 1. Try dividing the number 7 into equal groups. The only way you can do that is if you divided the 7 into 7 equal groups where each group has just 1 in it. So, if you were trying to divide 7 boxes of French fries equally, you would have to divide it into 7 groups where each group has only 1 box of French fries.

## Composite Numbers

Our next type of numbers are called composite numbers. A composite number is a number greater than 1 that can be divided by a number other than 1 and itself. Basically, composite numbers are positive numbers greater than 1 that are not prime numbers. Since 1 is a prime number, it is not a composite number. 2 is also a prime number, so it is not a composite number, either. Nor is 3 a composite number since it is also a prime number. However, 4 is a composite number because it is not a prime number.

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