Primes and rational numbers

Primes

A prime number (or simply a prime) is a whole positive number that has exactly two divisors: one and itself.
Number \(1\) is not a prime number, because it has a single divisor.
A composite number is any whole positive number that has more than 2 divisors; i.e., not \(1\) and not prime.

Rational numbers

A rational number is the ratio between two integers.
It is usually expressed as \(\dfrac{a}{b}\), where \(a\) is called the numerator and \(b\) the denominator of the rational number; the line between them is called the fraction bar.

Rational form

There are infinitely many equivalent rational numbers. For example, \(\frac{1}{2}=\frac{2}{4}=\frac{3}{6}=\cdots\). All equivalent rational numbers are considered one and the same number.
Integers are considered rational numbers with \(1\) as their denominator.
If the numerator of a rational number is smaller in absolute value than its denominator, the number is called a proper fraction; otherwise, it is called an improper fraction.