The README - File from the project:

!!!
IF YOU HAVE THE primenum-FOLDER FROM A STICK SO,
MOVE THE FOLDER TO ~/Downloads
!!!

Hello to primenum,

please follow next instructions:

-5. You have the primenum.tar.gz-file downloaded,
-3. You have decompress the tar.gz,
-2. You have open the decompressed folder,
-1. You have open the README file and you will follow the next instructions...
0. You will click a right click
1. You will enter the Context-Object >>Open in Terminal<<
2. Enter in the shell: sudo ./installer.sh
3. It cames...
4. Type in Terminal: primenum
5. Follow the information and ENJOY!!! :)

If you try a function twice, you will exit!
BUT: Itś not an bug! Itś a feature!