Not to discourage other answers, but you may want to look at previous examples of when this question was asked:

https://www.reddit.com/r/AskHistorians/comments/2sev0f/why_is_napoleon_referred_to_by_his_first_name/ https://www.reddit.com/r/AskHistorians/comments/26aru8/why_is_napoleon_not_referred_to_as_bonaparte/

and most recently here: https://www.reddit.com/r/AskHistorians/comments/6jipow/why_is_napoleon_commonly_referred_to_by_his_first/