I don't think it's feasible to calculate the leading digits of very large numbers. However, it's possible to narrow down the first digit in nondecimal bases. For example, Graham's number must start with 1 in base 3 because it's basically an exponential stack of 3's.
You can always calculate the ending digits using modular arithmetic.
Last fiddled with by ixfd64 on 20190131 at 18:02
