As of 2010, Harvard employs about 2,100 faculty to teach and advise approximately 6,700 undergraduates and 14,500 graduate and professional students. Eight US presidents have been graduates, and 75 Nobel Laureates have been student, faculty, or staff affiliates. Harvard is also the alma mater of sixty-two living billionaires, the most in the country. The Harvard University Library is the largest academic library in th US, and one of the largest in the world