Do you know the difference between prime and composite numbers? If not, don’t worry! You’ve come to the right place.
In this post, we’ll talk about what prime and composite numbers are and give you a handy chart you can use to quickly see if something is a composite number.
What Is a Composite Number?
Composite numbers are whole numbers that are greater than 1 and divisible by other whole numbers.
Here are the questions to ask yourself to decide if a number is composite:
- Is the number a whole number?
- Is the number greater than 1?
- Is the number divisible by whole numbers other than itself?
Let’s apply those questions to two different numbers to see if they are composite or not.
Take the number “4”.
4 is a whole number. It is greater than 1. You can divide 4 by 4. You can also divide 4 by 2, so it’s divisible by other whole numbers.
That means 4 is a composite number.
Let’s look at the number “3”.
3 is a whole number. It’s greater than 1. You can divide 3 by 3. But, you can’t divide 3 by any other whole numbers.
That means 3 isn’t a composite number.
How to Tell the Difference Between Prime and Composite Numbers
If a number isn’t composite, then it’s prime. Prime numbers are numbers that are greater than 1 that are only divisible by themselves and the number 1.
The best way to tell if a number is prime or composite is to perform the divisibility test.
When you use the divisibility test, you check to see if a number is divisible by common prime factors, like 2, 3, 5, 7, 11, and 13.
If you’re testing an even number, start by trying to divide it by 2 to see if it’s composite.
If you’re testing a number that ends with 0 or 5, try to divide it by 5.
If you get a whole number when dividing by any of these common factors, then your number is composite.
If you get a fraction or decimal when dividing by these common factors, then your number is likely prime.
Composite Number Chart (1-100)
Here is a handy composite number list to reference. All of the numbers in blue are composite numbers.
Prime Number Chart (1-100)
Here’s an easy-to-reference prime number list. All of the numbers in red are prime numbers.
Final Thoughts
It’s important to know whether a number is prime or composite so you can understand whether or not the number is divisible.
Remember, ask yourself these questions to tell if a number is a composite number or not:
- Is the number a whole number?
- Is the number greater than 1?
- Is the number divisible by whole numbers other than itself?
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