To answer the question a simple 6 digit number a few hows with an off the shelf brute force program. 10 to 20 digits could take a year if it's a good generator.

40+ digits good luck with that I doubt there's many on this site that would even know of the names of the software needed for that and far fewer outside of a 3 digit organization that has the time to dedicate a high end computer for the job.

It's just easier to get the information via social eng means or a $5 hammer to the knee caps.