I'm in My Prime, How About You? (1510)

Prime Numbers

This is one of those math topics that I honestly don’t use in my daily life, and have likewise forgotten the basics to what makes a number a prime number. I vaguely remembered that 5 and 7 were some of the first ones on the list, but I obviously needed a refresher when looking at the difference between a prime and composite number.

Here is a great interactive game that really gets the heart thumping and brain moving. Prime Shooter requires a person to have a quick reaction time. I found myself at the edge of my seat trying to shoot the prime numbers!

Dictionary.com defines our numbers as follows:

Prime number:

A positive integer that is not divisible without remainder by any integer except itself and 1, with 1 often excluded: For example, the integers 2, 3, 5, and 7 are prime numbers.

Composite Number:

A number that is a multiple of at least two numbers other than itself and 1.

To give a few examples of these types of numbers you can look at the list of numbers 2-10 as the number 1 is only divisible by itself.

2 - This is divisible only by the numbers 1 and 2, so it is a prime number

3 – This is divisible only by the numbers 1 and 3, so it is a prime number

4 – This is divisible by the numbers 1, 2, and 4 so it is a composite number

5 – This is divisible only by the numbers 1 and 5, so it is a prime number

6 – This is divisible by the numbers 1, 2, 3, and 6 so it is a composite number

7 – This is divisible only by the numbers 1 and 7, so it is a prime number

8 – This is divisible by the numbers 1, 2, 4, and 8 so it is a composite number

9 – This is divisible by the numbers 1, 3, and 9 so it is a composite number

10 – This is divisible by the numbers 1, 2, 5, and 10 so it is a composite number

Off of the top of my head, I use a shortcut to decide if a number is prime by seeing if it is an even number, which is obviously divisible by 2. I also think to myself on whether the number is easily divisible by 3, 5, and 7. (This obviously gets a little more difficult as the numbers get higher.) When your brain fails you, it is easy to do a quick search for a table online. I’m including a link that is helpful for this. 

Prime Numbers List

Don't be afraid of the math items that you haven't used for years. Embrace the challenge, do a little research and refresh that part of your brain!