What is a Prime number?
- Prime numbers are whole numbers greater than 1, that have only two factors 1 and the number itself.
- Prime numbers are divisible only by the number 1 or itself.
Prime number Example
For example, 2, 3, 5, 7, and 11 are the first few prime numbers.
- The factor of 2 is (1,2)
- The factor of 3 is (1,3)
- The factor of 5 is (1,5)
- The factor of 7 is (1,7)
Prime numbers up to 100
- List of all the prime numbers up to 100, marked in red.
Prime number – Properties
- p is prime if it has only two factors {1,p}
- 1 is not prime , as it has only one factor 1
- Every number can be decomposed into prime factors
Example: 12
- 12 = 2*2*3 = 22 *3
- 12 has factors 2 & 3.
- 2 & 3 are prime numbers
Example: 126
- 126 = 2*3*3*7 = 2*32 *7
- 126 has factors 2 , 3 & 7
- 2, 3, & 7 are prime numbers
- This decomposition is unique — it is known as prime factorization
