Create a chain of consecutive digits starting with 1 and following 9 by 0:
How many digits are needed to obtain the 1st prime number?
(In reply to computer exploration
Clearly 2 is not the correct answer, as it does not comply with the definition of the string (in which 9 is followed by 0).
Re your program - only the strings terminating by 1 and 7 are candidates to be tested, since 2,4,6,8 or 0 create an even number, 5 causes the chain to be divisible by 5, and 3 or 9 at the end result in s.o.d. that is a multiple of 3.
The answer (to the best of my knowledge) over 150 and below 200 digits, and I can provide it to you by Email if your revised rogram fails to discover it.
Feel free to reach me by Email for clarifications, if needed.