SAT Study Guide/Part 2 - The Math Section/General Numerical Concepts

Number properties There are several sets of numbers: Counting or Natural numbers are numbers that can be used to count real things: Integers (including 0) include the natural numbers and their opposites: Even integers are divisible by 2; you can express even integer as , where is any integer: Odd integers are not divisible by 2; you can express any odd integer as , where is any integer: Rational numbers are numbers you can express as a fraction , where and cannot simplify the other: Irrational numbers are non-repeating, non-terminating decimals that you cannot express as a ratio or division of intergers , where and cannot simplify the other: Real numbers include all of the above. Numbers can be prime. That is, they are divisible by themselves and one, only. 1 is not considered a prime number, and 2 is the only even prime number. The first eight prime numbers are: