Flight to the Lonesome Place — Alexander Key

On the run from killers, a boy genius looks for strength in numbers

When he steps on stage, Ronnie Cleveland feels his troubles slip away. He is the Blue Boy, a genius who sings, plays piano, and solves math problems faster than any calculator. His nightclub act is a great success, but he feels fear creeping into his heart. When a young Spanish girl warns him that trouble is coming, he knows she is right -- and that it's too late to stop it.
 
Before his time in the spotlight, Ronnie worked for a pair of underworld accountants. Because he remembers every number he ever crunched, the Blue Boy's head holds enough dirt to put the entire mob in jail -- and that makes him a target. When his manager and bodyguards disappear, Ronnie runs to find the mysterious girl, and seek refuge in the most lonesome place in the world.