Do I write 2 1/2 in numbers or two and half in letters. In a sentence.wikipedia
Proper grammar is not the question; it's a style question. The Chicago Manual of Style says in Press style, whole numbers from one through ninety-nine are spelled out, which may be followed by the words hundred, thousand, or million. In newspaper style, whole numbers from one through nine are spelled out. For titles, Two and a Half Men.