Update README.md

Author: heyitskbhere

README.md

@@ -124,6 +124,7 @@ It is very easy to contribute, you may follow these steps -
 97. [Streams API](./Programs/JavaStreams.java) - Program to demo the Java Stream API with String and Integer Lists.
 98.[Stack](https://github.com/PrajaktaSathe/Java/blob/main/Stack.java)-Program to demo the stack implementation
 99.[RotateLinkedList](https://github.com/PrajaktaSathe/Java/blob/main/Programs/RotateLinkedList.java)-Program to demo rotating a linked list
+100.Mersenne Prime
 # Contributors - 
 ## A big thank you to all our contributors!!!