The mathematical definition of a prime number is a number that has exactly two factors (no more or no less). Commonly though people think of prime numbers as being those that can only be divided exactly by 1 and by the number itself.
The number 7 is not exactly divisible by any number other than 1 and 7
It has two factors only; 1 and 7
Therefore, 7 is a prime number.
In other words, prime numbers have only 2 factors.
The first five prime numbers are; 2 , 3, 5 , 7 , 11
Prime Numbers Charts
The prime numbers up to 100 are highlighted in yellow on the chart below.
Is 1 a Prime Number?
The number 1 has only one factor so 1 is not a prime number.
A natural number that has more than two factors is called a composite number. In other words, a composite number has factors in addition to one and itself.
- All even numbers are divisible by two and so all even numbers greater than two are composite numbers.
- All numbers that end in five are divisible by five. Therefore all numbers that end with five and are greater than five are composite numbers.
- The numbers 0 and 1 are neither prime nor composite.
- If any whole number greater than 1 is not a prime number, then it is a composite number.
Prime or Composite?
|Number||Factors (or can be exactly divided by)||Composite or Prime?|
|2||1 , 2||Prime|
|3||1 , 3||Prime|
|4||1 , 2 , 4||Composite|
|5||1 , 5||Prime|
|6||1 , 2 , 3 , 6||Composite|
|7||1 , 7||Prime|
|8||1, 2 , 4 , 8||Composite|
|9||1, 3 , 9||Composite|
|10||1, 2 , 5 , 10||Composite|
|12||1 , 2 , 3 , 6 , 12||Composite|
|14||1, 2 , 7 , 14||Composite|
|15||1, 3 , 5 , 15||Composite|