The Prime Numbers
You can use divisibility rules to find prime numbers. Before we do that, can you define a prime number?
Goal:
Goal:
5, 13, and 23 are all prime numbers. Use the examples and explanations below to see if you can figure out what makes a number prime.
Example 1: Is 17 a prime number?
17 can be divided only by 17 and by 1. Therefore, 17 is a prime number.
Example 2: Is 36 a prime number?
36 can be divided only by 1, 2, 3, 4, 6, 9 and by 12. Therefore, 36 is not a prime number.
Question
So what do you think it means for a number to be prime?
A prime number can only be divided by itself and one.
Here you find a list of numbers, their factors and whether or not they are prime. Study this chart and develop a definition for Prime Numbers.
| Number |
Factors |
Prime? |
| 17 |
1, 17 |
Prime |
| 5 |
1, 5 |
Prime |
| 36 |
1, 2, 3, 4, 6, 9, 12, 18, 36 |
Not Prime |
| 13 | 1, 13 | Prime |
| 24 | 1, 2, 3, 4, 6, 8, 12, 24 | Not Prime |
So - what is your definition of Prime Number?
Answer: A prime number is a number with only two factors, 1 and the number itself.