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Prime numbers are special numbers that form the building blocks of mathematics. Understanding them helps us with multiplication, division, and many real-world applications like computer security.
What is a Prime Number? #
A prime number is a number that has exactly two factors: 1 and itself.
- Only Two Factors: Prime numbers can only be divided evenly by 1 and themselves
- Greater Than 1: 1 is not a prime number because it only has one factor
- No Patterns: Prime numbers don’t follow a simple pattern
Prime Numbers Under 50 #
2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47
How to Check if a Number is Prime #
- Check if the number is greater than 1
- Try dividing it by numbers from 2 up to its square root
- If none of these divisions give a whole number, it’s prime
Example: Is 17 prime? #
- 17 ÷ 2 = 8.5 (not divisible)
- 17 ÷ 3 = 5.67 (not divisible)
- 17 ÷ 4 = 4.25 (not divisible)
- Square root of 17 is about 4.12, so we can stop here
- Therefore, 17 is prime!
