Riot IDs, which is also your Valorant name, need to be at least 3 letters and up to 16 letters long. They can be alphanumeric, so you have a lot of room to play with. However, remember that names that are offensive and violate Valorant's code of conduct can be reported and go through an automated check process. If a player is found to be in violation of this rule, they can be forced to change their name the next time they log into their account.