Once a week I require my students to write up several problems using correct grammar. Yesterday I wrote this on the overhead.
1 is the loneliest number.
I asked the class what was wrong with this sentence. No response. Many of my students don’t know that it is ungrammatical to start a sentence with a numeral – see rule 16 on this useful web page.
My student Sam asked if we couldn’t rewrite the sentence to be “The loneliest number is one.” I said yes but it wouldn’t make as good a song.