Italics and Quotation Marks
Q. Should numerals and spelled-out numbers be italicized if they’re being referred to as numbers, as in “The number twelve is significant in the Old Testament”? What about a personal name being referred to as a name?
A. In either case, italics are unnecessary. Write “the number twelve” (or “the number 12”; see CMOS 9.3 for Chicago’s alternative rule for spelling out numbers) and, for example, “the name Ruth.”
Italics (or quotation marks) for words or letters used as such are designed to prevent misreading the word or letter as literally part of the grammatical sentence; no such ambiguity is likely with numbers or names. So, for example, the following sentence could be ambiguous without italics or quotation marks:
The word search was starting to bother me.
On the other hand, special treatment may be necessary for names or numbers in certain cases:
Type “Ruth” into the search box, then hit Enter.