Correct. 5 is the answer. I would have agreed with you on the maximum number alive at once logically would have occurred in the twentieth century, but here is why we were both wrong.
20th Century: T Roosevelt(almost), Wilson, Eisenhower, Reagan, Clinton(maybe) will have 2 terms plus FDR had 3+ terms. Plus many of the Presidents this Century died shortly after leaving office. Plus, remember, we know there are at least 5 future alive today, but there is probably a few more(because of 1 termers, death in office, and the 2036/2040 winners are probably alive right now as well)
In the 1830s to 1884, you had VanBuren, Harrison, Tyler, Polk, Taylor, Fillmore, Pierce, Buchanan, Johnson, Hayes, Garfield, Arthur ...all 1 termers or less. After Jackson, US Grant was the next President who served two full terms. So, with the old timers that were still alive plus all the FUTURE 1 term Presidents just born, that is why so many were alive at once.
TG |
