Prithvi Shaw is the 4th youngest to score a ton on debut and the 7th youngest test centurion ever.
He became the second Indian among those seven today joining a certain Sachin Tendulkar, who is at No.2. The eight youngest test centurions have the most representatives from Pakistan , followed by India  and one each from Bangladesh and Zimbabwe.
Shaw is the 21st male cricketer to score a first test hundred while still in his teens. Age wise, he is 7th on the list which also includes the likes of Javed Miandad, Aravinda DeSilva and Graeme Pollock.