# 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!

Here is a list of all of the skills that cover number theory! To start practicing, just click on any link.

## Fifth-grade skills

- A.9 Even or odd: arithmetic rules
- F.1 Prime and composite numbers
- F.2 Prime factorization
- F.3 Prime factorization with exponents
- F.4 Divisibility rules
- F.5 Divisibility rules: word problems
- F.6 Greatest common factor
- F.7 Greatest common factor of three numbers
- F.8 Least common multiple
- F.9 Least common multiple of three or four numbers

## Sixth-grade skills

- C.1 Divisibility rules
- E.3 Prime or composite
- E.4 Identify factors
- E.5 Prime factorization
- E.6 Prime factorization with exponents
- E.7 Greatest common factor
- E.8 Greatest common factor of three or four numbers
- E.9 Least common multiple
- E.10 Least common multiple of three or four numbers
- E.11 GCF and LCM: word problems
- E.12 Sort factors of numerical expressions
- E.13 Classify numbers
- Y.8 Sort factors of variable expressions

## Seventh-grade skills

- A.1 Prime or composite
- A.2 Prime factorization
- A.3 Multiplicative inverses
- A.4 Divisibility rules
- A.5 Greatest common factor
- A.6 Least common multiple
- A.7 GCF and LCM: word problems
- A.8 Sort factors of numerical expressions
- A.11 Classify numbers
- H.4 Identify rational numbers
- R.9 Sort factors of variable expressions

## 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 Sort factors of numerical expressions
- A.9 Classify numbers
- D.5 Identify rational and irrational numbers
- E.1 Reciprocals and multiplicative inverses
- V.11 Sort factors of variable expressions