The Chicago Manual of Style recommends spelling out the numbers zero through one hundred and using figures thereafter—except for whole numbers used in combination with hundred , thousand , hundred thousand , million , billion , and beyond (., two hundred ; twenty-eight thousand ; three hundred thousand ; one million ). In Chicago style, as opposed to AP style, we would write four hundred , eight thousand , and twenty million with no numerals—but like AP, Chicago style would require numerals for 401 ; 8,012 ; and 20,040,086 .
If you are willing to write an academic essay or a research paper, you need to follow a standardized documentation style. APA or American Psychological Association style of writing is one of the most common and practiced documentation techniques, used globally by students, researchers and independent writers. An APA style essay requires predefined methods to be followed in reference citation, text formatting, heading placement, figure depiction, arrangement of annotations and appendices. There are many other standard documentation techniques like MLA, Harvard, Turabian, etc., but, APA is the most common one in practice. This article will elaborate some very basic rules defined for writing in APA style.