How to Classify Numbers
To classify a number, check the sets from narrowest to widest: natural numbers (1, 2, 3, …), whole numbers (0, 1, 2, …), integers (… −2, −1, 0, 1, 2 …), rational numbers (any fraction of integers), and irrational numbers (like √2 and π); together the rational and irrational numbers make up the real numbers. […]