I wrote this code to find 21 digit prime palindrome in decimals of pi. I found it at position 140,672,630,233 in pi and the desired number was: 151978145606541879151. We need 1 byte to store 1 pi digit in txt file. It will require 93 GB to store 100 Billion digits of pi. Calculation of pi digits can be done via y-cruncher on any windows or linux system. It may take about 10 hours to calculate 100 Billion pi digits on a normal pc. Alternatively one can download pi digits from online sources. You may need to split the files in 500 MB or 1 GB chunks. You can use Git Bash to split the files. Use the command on Git Bash: split "file_location" -b 500m
A normal pc may take about 10 hours to find the 21 digit prime palindrom in pi. The code is written in such a way that you can use multiple pc to find. You don't have to start from 0.