Factor: A whole number that divides evenly into another whole number.
Example: 3 and 4 are factors of 12 because 12 ÷ 3 = 4
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Prime Number: A whole number that can only be divided evenly by 1 and itself (that is, it has only 2 factors).
Example: 5 is a prime number because it can only be divided evenly by 1 and 5
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Composite Number: A whole number than can be divided evenly by more than 2 factors
Example: 10 is a composite number because it can be divided evenly by 1, 2, 5 and 10
Source: Kerrie Meagher