- Prime Numbers Factors and Multiples
- Home
- Even and Odd Numbers
- Divisibility Rules for 2, 5, and 10
- Divisibility Rules for 3 and 9
- Factors
- Prime Numbers
- Prime Factorization
- Greatest Common Factor of 2 Numbers
- Greatest Common Factor of 3 Numbers
- Introduction to Distributive Property
- Understanding the Distributive Property
- Introduction to Factoring With Numbers
- Factoring a Sum or Difference of Whole Numbers
- Least Common Multiple of 2 Numbers
- Least Common Multiple of 3 Numbers
- Word Problem Involving the Least Common Multiple of 2 Numbers

- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who

# Prime Numbers

### Prime numbers

A number is a **prime number** if its only factors are 1 and itself.

7 is a prime number. Its factors are 1 and 7 itself

Some **examples** of prime numbers are 2, 3, 5, 7, 11, 13 and so on.

2 is the only even prime number. All other prime numbers are odd numbers

### Composite numbers

If a number has three or more factors, it is a **composite number**. A number which has factors in addition to one and itself is called a composite number.

6 is a composite number. It has four factors; 1, 2, 3 and 6

For **example**: 4, 6, 8, 9, 10, 12,...are examples of some composite numbers

All even numbers except 2 are composite numbers.

**Neither Prime nor Composite**

0 and 1 are neither prime numbers nor composite numbers.

State whether each number in table below is prime or not.

### Solution

**Step 1:**

**Step 2:**

Of the given numbers 18, 28 and 35 have three or more factors. So they are not prime but composite numbers.

**Step 3:**

The numbers 5, 23 and 31 have only 1 and themselves as factors. So these numbers are prime numbers.

State whether each number in table below is prime or not.

### Solution

**Step 1:**

**Step 2:**

Of the given numbers 21, 27 and 38 have three or more factors. So they are not prime but composite numbers.

**Step 3:**

The numbers 13, 29 and 43 have only 1 and themselves as factors. So these numbers are prime numbers.