The Notable Numeral

Everything About Fiction You Never Wanted to Know.
"Wait, if you're the H.I.V.E. Five, why are there six of you?"
Kid Flash, Teen Titans

If you have a group of people banding together to fight evil, or to cause it, then it's good to have a good team name that people will remember. If you can't think of anything else, then why not name yourself after the number of members you have, plus a nice adjective that describes you? Maybe try to tie it together in a pun or something.

In the end, what do you have? Why, The Notable Numeral, of course!

This naming convention is popular in Real Life to describe people who make the news as a group, usually as either the victims of a crime or as the people arrested for a crime (often in historic/sensational cases of people who are believed to be wrongly accused, whose case seems to represent a broader issue or who grab the public's attention in some other way), such as the Buffalo Six and the West Memphis Three. The Other Wiki calls these "Enumerated defendants." Describing a single such defendant, usually fictional, as the something-or-other One is a Stock Parody.

Beware, if excess alliteration disturbs you, then it might be best to look elsewhere.

See also The Adjectival Superhero, where the adjective describes a person or team instead of a number. Can cross with Superhero Sobriquets if it's a nickname and not the team's proper name.

Examples (Numerically Ordered For Your Convenience):