How many US presidents were alive over the last 100 years?

Over the last 100 years, there have been 17 U.S. presidents, from Calvin Coolidge, who took office in 1923, to Joe Biden, who began his presidency in 2021. Since the question pertains to those alive during this period, it includes all presidents who served and were living at any point over the last century. As of October 2023, five of those presidents are still alive: Jimmy Carter, Bill Clinton, George W. Bush, Barack Obama, and Joe Biden.