# Is 1 a Prime Number?

**Prime Number Posters** – Is one a prime number? A simple test to see if a number is prime.

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**Is 1 a Prime Number?**

**Is 1 a Prime Number?**

**No! One is NOT a prime number!**

I usually try to introduce the concept of 1 not being prime by examining the mathematical definition… very closely.

**‘For a number to be prime it must have TWO distinct (different) factors’. Ham up the word TWO. Use a funny voice.**

In 1’s case, its factors are 1 and 1.

**For a number to be prime it must be able to be divided by itself AND 1. Ham up the word AND. Use a funny voice.**

In the case of 1 ‘itself ‘ **IS** one.

This poster can then be added to your Math Vocabulary Display as a form of Math Help or reference material 🙂

**What is a Prime Number?**

Here is a simple test you can do to work out if a number is prime. e.g. Is 11 prime? Is 21 prime? etc

Use blocks to see if the poster below helps your students identify prime numbers.

You might also like to have a look at…

– What is a prime number?

– Is two a prime number?

– a list of prime numbers

– The technical reason what 1 is not prime

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