What do you call a number that can't keep still?

The joke “What do you call a number that can’t keep still? A roamin’ numeral” is a pun that combines mathematical terminology with wordplay. “Roaming” means to move around freely without a fixed direction or purpose. The term “Roman numeral” refers to the numeric system used in ancient Rome, which uses letters to represent numbers (for example, I for 1, V for 5, X for 10, etc.). The humor comes from substituting “Roman” with “roamin'” to create a whimsical image of a number moving around, as if it were a person wandering without staying in one place, hence a “roamin’ numeral.”