Joseph Biden, President no 46, was born on 20/11/1942. When sworn in on 20/01/2021, he was at 78+ the oldest to be sworn in as President. The previous record was held by Ronald Reagan (b. 06/02/1911) when sworn in for the second time on 20/01/1985. He was then almost 74.
The oldest President to be sworn in for the first time was Donald Trump (14/06/1946) who was 70+ when sworn in on 20/01/2016. Earlier it was Reagan who was almost 70 when sworn in on 20/01/1981.
At one time it was felt that Bernard Sanders might be elected President. Born on 08/09/1941, he is over a year older than Biden and would have set the same records.
Biden is the second Catholic President (after JFK) and the second to be born in Pennsylvania (after James Buchanan of 1857-1861), the predecessor of Abraham Lincoln. Buchanan figures quite high in the rankings of “Worst President”, though Trump may ultimately get this title. See: https://en.wikipedia.org/wiki/Historical_rankings_of_presidents_of_the_United_States
The US has not had a First Gentleman yet, though Bill Clinton came close to it in 2016. Now there is a Second Gentleman, who is Jewish for good measure.
Kamala Harris was born in Oakland, CA in 1964. She has a chance of becoming President in 2025 (or earlier, if Tippecanoe’s Curse reappears). She would then be the second President after Nixon to be born in CA.