Saturday, 09 September 2006 ©RSH

Number

Prime Numbers and Prime factors

Saturday, 09 September 2006 ©RSH

Prime Numbers• A prime number has exactly 2 factors, 1 and

itself.• 1 is not a prime number.• The first five prime numbers are:

2, 3, 5, 7, and

Prime Numbers• A prime number has exactly 2 factors, 1 and

itself.• 1 is not a prime number.• The first five prime numbers are:

2, 3, 5, 7, and

Notes

11

Prime numbers are used in computer security – for passwords and credit cards !

Saturday, 09 September 2006 ©RSH

Prime Factors• The factors of 12 are: 1, 2, 3, 4, 6, 12• The prime factors of 12 are 2 and 3 because

these are the only prime numbers in the list.

Prime Factors• The factors of 12 are: 1, 2, 3, 4, 6, 12• The prime factors of 12 are 2 and 3 because

these are the only prime numbers in the list.

Notes

Saturday, 09 September 2006 ©RSH

Exercise1. Write down all the prime numbers between 10

and 30.

2. Write down two prime numbers which add up to another prime.

11, 13, 17, 19, 23, 29

2 + 3 = 5 or 2 + 5 = 7

3. Write down the prime factors of 8.

2