# Number theory

Here is a list of all of the skills that cover number theory! These skills are organized by grade, and you can move your mouse over any skill name to preview the skill. To start practicing, just click on any link. IXL will track your score, and the questions will automatically increase in difficulty as you improve!

## Eighth-grade skills

- A.1 Factors
- A.2 Divisibility rules
- A.3 Prime or composite
- A.4 Prime factorization
- A.5 Greatest common factor
- A.6 Least common multiple
- A.7 GCF and LCM: word problems
- A.8 Classify numbers
- D.5 Identify rational and irrational numbers
- E.1 Reciprocals and multiplicative inverses
- V.10 Sort factors of expressions