Types of Numbers
1. Natural Numbers
Numbers from 1 and go on: 1, 2, 3, 4, 5, …
2. Whole Numbers
Natural numbers plus 0: 0, 1, 2, 3, …
3. Integers
Positive, negative numbers and 0: … -3, -2, -1, 0, 1, 2, …
4. Even Numbers
End with 0, 2, 4, 6, 8: 2, 4, 6, 8, 10, …
5. Odd Numbers
End with 1, 3, 5, 7, 9: 1, 3, 5, 7, 9, …
6. Prime Numbers
Only 2 factors: 2, 3, 5, 7, 11, …
7. Composite Numbers
More than 2 factors: 4, 6, 8, 9, …
8. Rational Numbers
Can be written as fractions: 1/2, 3/4, 5/1
9. Irrational Numbers
Cannot be written as fractions: √2, π
10. Decimal Numbers
Contain a dot: 3.5, 2.75, …
11. Roman Numbers
Old-style: I, V, X, L, C
Fun Facts: 0 is neither positive nor negative. 2 is the only even prime. Numbers go on forever (∞).