<p>I don’t want to brag or nothin’ but my grandfather became president of Ogden College in Kentucky (now part of WKU) when he was 23. I am also reasonably sure that there have been math professors younger than 19 over the course of the centuries. Norbert Wiener, for instance, pulled down his Ph.D. from Harvard when he was only 18, though it seems he didn’t teach until a few years later.</p>