Also called the “Prophet, Seer, and Revelator,” or the living prophet. They believe that he, and he alone, receives direct revelations for the entire church. These revelations take precedence even over their written scriptures. It is a lifetime position. The apostle with the longest tenure becomes the church president at the death of the current church president.
“Our greatest safety lies in strictly following the word of the Lord given through His prophets, particularly the current President of the Church. The Lord warns that those who ignore the words of the living prophets will fall. He promises great blessings to those who follow the President of the Church.” (lds.org)