3:17 What are Prime Numbers and Composite Numbers?
Crisp UK GCSE-aligned explainer defining prime numbers and how to test if a number is prime.
Prime numbers
Recognise and recall the 2-digit prime numbers
4 hand-picked video lessons for this topic, each checked for relevance and clarity, graded by difficulty and labelled by depth. Press play to watch — nothing loads from YouTube until you do.
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4 shown 3:17 
4:46 What are Prime Numbers? | Math with Mr. J
Clear, friendly walkthrough of what makes a number prime with plenty of worked examples.
3:31 Prime Numbers
Trusted UK channel gives the definition and lists the prime numbers up to 31.
3:38 Finding Prime Numbers
Uses the Sieve of Eratosthenes so you can find and recall every prime up to 100.