Just check for the existence of at least one odd digit mod 10^B for some well chosen B. Here is a C program that does the verification up to 2^(10^10) in 30 se

Just check for the existence of at least one odd digit mod 10^B for some well chosen B. Here is a C program that does the verification up to 2^(10^10) in 30 seconds: https://gist.github.com/fredrik-johansson/8924e10e5d74e391094893932914c852 https://gist.github.com/fredrik-johansson/8924e10e5d74e39109... Edit: made it multithreaded, goes up to 2^(10^12) in nine minutes on 8 cores.