The line chart below shows when the longest prime numbers were discovered. Because the lengths vary greatly, a log axis is used.
The longest known prime number was discovered on Dec 26th, 2017 with a length of 23,249,425 digits, nearly 1 million digits longer than the previous record. The accelerated discovery of prime numbers is largely due to computing power and distribute computing projects like GIMPS.
This chart was built with the Aploris add-in for PowerPoint on a Mac.