What prompted Pharaoh to ask Ya'akov's age?
Ramban, Hadar Zekenim and Rashbam: Because he looked way beyond his hundred and thirty years. 1
Moshav Zekenim #1: Yakov said that if Paro will let him return to his origin after the famine ends, fine. If not, I will return [now] and buy from Yosef. Paro asked, at your age, do you expect to live so long - how old are you?
Moshav Zekenim (10) #2: In Paro's youth, he went to Avimelech to learn Derech Eretz, and saw Yitzchak. He now thought that Yakov is Yitzchak, and was astounded that he is still alive.