In this video, we're going to look at the difference between prime numbers and composite numbers. A prime number is any number that can only be divided by itself and one a whole number of times. So basically its only factors are one and itself.
Although there is an exception to this, which is that one doesn't count as a prime number. The number 2 is a prime number though, because its only factors are 1 and 2. 3 is also a prime number, because it can only be divided by 1 and 3. The number 4 though isn't prime, because it can be divided by 2 as well as 1 and 4. 5 is prime, and 6 isn't prime, as it's divisible by 3, or 2 as well as 1 and 6. Other prime numbers include 7, 11, 13, 17, 19, 23 and 29, with the list continuing on and on. One thing you might have noticed is that 2 is the only even prime number. This is because all other even numbers are divisible by 2, which means that they can't be prime.
Now there's not really any easy way to find out if a number is prime or not. You basically just have to keep trying to divide it by things and see if any of them work. For example, if we took the number 17 we could think to ourselves is this a multiple of two?
No. Is it a multiple of three? No. And so on. working our way through the numbers until we're happy that it's not divisible by any whole numbers except 1 and 17. Now a composite number is basically any number that isn't prime, but again 1 is the exception and isn't a composite number either, so 6 would be a composite number.
because it's not a prime number. Or in other words, it's divisible by numbers other than 1 and 6, in this case 2 and 3. So numbers like 4, 8, 9 and 10 would also be composite numbers, because none of these are prime. Anyway, that's everything for this video.
So I hope that makes sense and we'll see you next time.