Ian says: "21 is a prime number"
Is Ian correct?
You must give a reason for your answer.
Practise Edexcel IGCSE Maths Factors and Multiples with exam-style questions for IGCSE Maths. 24 questions, matched to the Edexcel IGCSE Maths (4MA1) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.