Concept 2 of 8Foundation
Watch on YouTubeVideoPrime vs composite numbers
A prime has exactly 2 factors: 1 and itself. A composite has more than 2.
First primes: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31…
- ⚠️ 1 is NOT prime (only 1 factor).
- ⚠️ 2 is the only even prime. All other evens are divisible by 2.
- Twin primes differ by 2: (3,5), (5,7), (11,13), (17,19), (29,31).
- Co-primes: HCF is 1 (e.g. 8 and 15 are co-prime).
Example
Is 51 prime? 51 = 3 × 17 → composite.
Is 53 prime? Check primes up to √53 (~7): not divisible by 2, 3, 5, 7 → prime!
Is 53 prime? Check primes up to √53 (~7): not divisible by 2, 3, 5, 7 → prime!
💡 Tip:To check if N is prime, test division by primes up to √N.
▶Prefer a video? Open YouTube search for “prime and composite numbers class 6”↗🎯 Try it!
5 questions to check what you just read.
0 / 5
- Q1.Which is prime?
- Q2.Smallest composite number:
- Q3.Is 1 prime?
- Q4.Twin primes below 20:
- Q5.Is 51 prime?