The file primes_list.txt is big! The zipped file is 1.13 GB. The raw (unzipped) file is over 4.8 GB and is 455,052,511 lines long. That's how many prime numbers there are between 1 and 10 billion. You will not be able to open this file with normal text editors (Notepad, Notepad++, ...). I'm told that Wordpad will open a file of any size, but you will not want to wait for Wordpad to load this file. Trust me. A good option is Glogg (http://glogg.bonnefon.org/). It's not a text editor, it's just a text viewer. However, it loads large files like primes_list.txt very quickly and can also very quickly search the file. Jake - December 28, 2020