As of the time of writing, there is no information available regarding the number of teams participating in today's Atalanta match. It is possible that this information may be released closer to the game date.

However, it is important to note that football matches can feature multiple teams competing, depending on the league or competition being played. In Italy, for example, Serie A is made up of 20 teams, with each team playing 38 games against other teams within their division during the season.

In addition to Serie A, there are also other leagues and competitions in which football matches may feature multiple teams competing. For example, in Spain, La Liga has 19 teams, while in England, the Premier League has 20 teams.

It is also worth noting that some football matches may only involve two teams competing, such as in the case of a cup final or a friendly match. However, if you have any specific details about the upcoming match at Atalanta, I would be happy to provide more information based on the information available.