example, 21, 4, 0, and −2048 are integers. 2. Whole Numbers: Counting number that starts with zero: 0,1, 2, 3,..... 3. Prime Numbers: A number that is divisible only by itself and 1 4. Composite Numbers: A whole number that can be divided evenly by numbers other than 1 or itself. 5. Rational Numbers: A rational number is any number that can be expressed as the quotient or fraction p/q of two integers 6. Irrational Numbers: If written in decimal notation, an irrational number would have an infinite number of digits to the right of the decimal point, without repetition. 7. Real Numbers: Combination of rational and irrational numbers I hope you enjoy this online lecture on ""Introduction to Real Number System "" by LetsTute.