I always believed that the Apostles were the original 12 plus the replacement for Judas. There are some, mostly Protestant, who refer to Paul as an apostle. Does the Church consider Paul to be an apostle?
St. Paul was not one of the twelve. But since he considered himself to be an Apostle, certainly the Catholic Church does as well. For more on him, see:
*]Saint Paul[/LIST] Fr. Vincent Serpa, O.P.