Erdös published more than 1,500 papers and did mathematics 19 hours a day, even at 83 – "The 1st sign of senility is when a man forgets his theorems. The 2ns sign is when he forgets to zip up. The 3rd sign is when he forgets to zip down" pic.twitter.com/gsG231pINM
— Fermat's Library (@fermatslibrary) November 5, 2020