Somebody else may point this out, but Paul was not an Apostle.
An early convert, and a very effective proponent of the early Church to the Gentiles, but not an Apostle. (In fact, tradition maintains he held the cloaks of those Jews who stoned the first converts.)
"Paul, a slave of Christ Jesus, called to be an apostle and set apart for the gospel of God." Romans 1:1.
Paul was an apostle. He just recieved his calling in a different manner than the other apostles.
See also Galatians 2:11 - 24.
1 Corinthians 9:1 Am I not free? Am I not an apostle?