Prime or Composite
Part of the Factors & Fractions section of Coddy's Pre-Algebra journey. Lesson 4 of 56.
Is 91 prime? Most adults say yes. It is odd, it does not end in 5, and it is not in the times tables they remember.
A prime number has exactly two factors: 1 and itself. 2, 3, 5, 7, 11 and 13 are primes. A number with more factors is called composite.
1 is neither, because it has only one factor. 2 is the only even prime.
To test a number, try dividing it by 2, 3, 5 and 7.
Challenge
Exactly one of these numbers is prime. Which one?
Try it yourself
Choose the best answer
All lessons in Factors & Fractions
1Factors and Multiples
What a Factor IsDivisibility RulesMultiplesPrime or CompositeRecap: Factors and Multiples4What a Fraction Is
Parts of a WholeFractions on the LineA Fraction of a NumberImproper FractionsRecap: What a Fraction Is7Multiplying Fractions
Top Times TopCancel FirstWhole Times FractionA Fraction of a FractionRecap: Multiplying Fractions10Fractions in Stories
Part of a GroupWhat Is LeftSharing a FractionScaling a RecipeRecap: Fraction Stories5Equivalent Fractions
Same Amount, New NameSimplifying FractionsSimplify in StepsComparing FractionsRecap: Equivalent Fractions