🔢 Prime Numbers and Composite Numbers
Prime numbers are special numbers 🌟. They have only two friends that can divide them exactly: 1 and themselves.
🤔 What does that mean?
- A prime number can be shared only by 1 and itself.
- If more numbers can share it, then it is not prime.
✅ Prime Numbers (Examples)
2
3
5
7
11
13
17
19
23
29
⭐ 2 is special — it is the only even prime number!
❌ Not Prime Numbers
These numbers have more than two friends/factors:
4
6
8
9
10
So, these numbers are instead called composite numbers.
Example: 6 can be shared by 1, 2, 3, and 6 — so it is not prime. It gets composite number award.
1 is either prime nor composite (it has only one friend/factor).
💡 Easy Tip to Remember:
If a number can be divided only by 1 and itself, it is a prime number!
If a number can be divided only by 1 and itself, it is a prime number!
🎯 Try This!
Is 7 a prime number? 🤔
Can you find all the prime numbers between 1 and 20?
Is 7 a prime number? 🤔
Can you find all the prime numbers between 1 and 20?
🤔 Interactive Activity
Try sharing numbers with different friends to see which ones can only be shared by 1 and themselves.
Try sharing numbers with different friends to see which ones can only be shared by 1 and themselves.
🏴☠️ Crack the Treasure Lock!
A pirate chest is locked with a secret number.
You can only ask questions about grouping the number.
🔐 Rule:
You may ask:
“Can the number be shared equally into ___ groups?”
Example 1: Easy Lock (Not Prime)
Secret number: 12
✔ Can it be shared into 2 groups? YES
✔ Can it be shared into 3 groups? YES
✔ Can it be shared into 4 groups? YES
➜ The lock gives lots of clues. Easy to crack!
Secret number: 12
✔ Can it be shared into 2 groups? YES
✔ Can it be shared into 3 groups? YES
✔ Can it be shared into 4 groups? YES
➜ The lock gives lots of clues. Easy to crack!
Example 2: Tricky Lock (Prime)
Secret number: 13
❌ Can it be shared into 2 groups? NO
❌ Can it be shared into 3 groups? NO
❌ Can it be shared into 4 groups? NO
➜ Very few clues. Hard to crack!
Secret number: 13
❌ Can it be shared into 2 groups? NO
❌ Can it be shared into 3 groups? NO
❌ Can it be shared into 4 groups? NO
➜ Very few clues. Hard to crack!
🎯 Your Turn!
The treasure lock uses the number 17.
Can it be shared equally into:
The treasure lock uses the number 17.
Can it be shared equally into:
- 2 groups?
- 3 groups?
- 4 groups?
💡 Answer:
17 cannot be shared equally into 2, 3, or 4 groups.
It only works with 1 group or 17 groups.
➜ 17 is a prime number, which makes the treasure lock tough to open!
17 cannot be shared equally into 2, 3, or 4 groups.
It only works with 1 group or 17 groups.
➜ 17 is a prime number, which makes the treasure lock tough to open!
⭐ Key Idea:
Prime numbers make guessing games harder because they give very few clues.
So, prime numbers is used when locking secret codes or passwords in a computer.
So, prime numbers is used when locking secret codes or passwords in a computer.