Types of Number

Prime Numbers Prime numbers are numbers that only divide by themselves and 1 1 is not a prime number because it can only be divided by 1 2 is the only even prime number because all even numbers can be divided by 1, 2 and themselves 5 is the only prime number that ends in 5

Prime Numbers 2,3,5,7,11,13,17,19,23,29,31,37,41,43 Apart from 2 all the above numbers are odd Apart from 5 they do not end in 5 None of these numbers end in 0 (10, 20, 30 etc. can all be divided by 10) Apart from 2 and 5 all prime numbers end in 1, 3, 7 or 9

Square numbers This is the sequence when numbers are squared (2 dimensions) 1 x 1= 1, 2 x 2= 4, 3 x 3= 9, 4 x 4= 16, 5 x 5= 25, 6 x 6 = 36, 7 x 7= 49, 8 x 8 =64, 9 x 9= 81, 10 x 10 = 100 You can find out if a number is a square number by square rooting it, e.g. √144 = 12

Cube Numbers This is the sequence when numbers are cubed (3 dimensions) 1 x 1 x 1= 1, 2 x 2 x 2= 8, 3 x 3 x 3= 27, 4 x 4 x 4= 64, 5 x 5 x 5= 125, 6 x 6 x 6= 216, 7 x 7 x 7= 343, 8 x 8 x 8= 512, 9 x 9 x 9= 729, 10 x 10 x 10= 1,000 To cube a number on the calculator you type in 2 Xy 3 (which equals 8) To find out if it is a cubed number you would type 125 X1/y 3 (which equals 5)

Triangle Numbers These are the numbers you would need to make triangles, starting with 1 1, 3, 6, 10, 15, 21, 28, 36, 45, 55 2 3 4 5 6 7 8 9 10 The difference between triangle numbers is easy to recognise

Questions What is the sequence of numbers: 36,49,64,81? Square Numbers What are the first five prime numbers? 2,3,5,7,11 Is 71 a prime number? Find the square root of 71 It is 8 Does 71 divide by 2,3,5 or 7 No, so 71 is a prime number