Twenty-one has special meaning to me. If you were my daughter would you mind if I had named you Twenty-One?
Seven seems to work because it sounds like
Kevin Devin and
Evan, and because it's got a rep as a lucky or magic number. There's a symbolic meaning when it's an
amount of something. Seven sins, seven seas, seven sisters etc. I just don't like it as a name because ... well, it's
still a number. Sorry, I just can't get over it. Whatever, though - there are far worse names being used more often.