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Prime and Composite Numbers

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Prime Numbers

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

Click here for a chart listing prime numbers up to 251

Is 1 a Prime Number?

The number 1 has only one factor so 1 is not a prime number.

Composite Numbers

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.

  1. All even numbers are divisible by two and so all even numbers greater than two are composite numbers.
  2. 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.
  3. The numbers 0 and 1 are neither prime nor composite.
  4. 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
11 1, 11 Prime
12 1 , 2 , 3 , 6 , 12 Composite
13 1, 13 Prime
14 1, 2 , 7 , 14 Composite
15 1, 3 , 5 , 15 Composite

Try our fun Prime or Composite math game and also have a go at the Factors - Prime and Composite Numbers worksheets below.

Prime/ Composite Worksheets

 

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