Prime numbers

What is a prime number?

A prime number is any number which only has two factors: 1 and itself.

Examples of prime numbers

2 (factors: 1, 2)
3 (factors: 1, 3)
5 (factors: 1, 5)
29 (factors: 1, 29)
97 (factors: 1, 97)

Non-examples of prime numbers

4 (factors: 1, 2, 4) - three factors
6 (factors: 1, 2, 3, 6) - four factors
9 (factors: 1, 3, 9) - three factors
15 (factors: 1, 3, 5, 15) - four factors
1 (factors: 1) - only one factor
6.5 - not prime as it is not an integer (whole number)

Composite numbers

You may think that all non-prime numbers are composite numbers, and you’d be right… usually.

The number 1 has only one factor: 1, so it is not prime because it does not have 2 factors.
It is also not composite, because composite numbers have more than 2 factors.

flashcards

Question	Answer
What is a prime number?	A prime number is any number which only has two factors: 1 and itself.
Give an example of a prime number.	2 (factors: 1, 2)
Give an example of a prime number.	3 (factors: 1, 3)
Give an example of a prime number.	5 (factors: 1, 5)
Give an example of a prime number.	29 (factors: 1, 29)
Give an example of a prime number.	97 (factors: 1, 97)
Give a non-example of a prime number and explain why.	4 (factors: 1, 2, 4) - three factors
Give a non-example of a prime number and explain why.	6 (factors: 1, 2, 3, 6) - four factors
Give a non-example of a prime number and explain why.	9 (factors: 1, 3, 9) - three factors
Give a non-example of a prime number and explain why.	15 (factors: 1, 3, 5, 15) - four factors
Why is 1 not a prime number?	It has only one factor: 1, so it does not have 2 factors.
Is 6.5 a prime number? Why?	No, it is not prime as it is not an integer (whole number).
Why is 1 not a composite number?	Composite numbers have more than 2 factors, but 1 has only one factor.