What does Galatians 1:21 mean?

Writing to Christians in Galatia, Paul continues to show, using his personal story, why the group known as Judaizers are wrong about him. This sect had been saying Paul was not qualified to call himself an apostle. The role of apostle was a significant one reserved for those who had seen Jesus and who had been sent out by Him. The Judaizers seem to have been saying that Paul was merely trained by other apostles and was therefore lying about his status and authority.

Paul has gone to lengths to show that he only had brief contact with Peter and Jesus' brother James, and only some three years after his conversion. The apostles did not train him. Paul, in fact, saw Jesus Himself and was sent out to preach to the Gentiles by Jesus. He was truly an apostle and his message was trustworthy.

In fact, Paul says, after meeting with Peter and James, he went to preach in Syria and Cilicia, far from where the apostles were in Jerusalem. In the next verse, he will make the point that they didn't even know him personally until after that. They were not his teachers; Christ was.