a buddy of mine likes to post hard math questions on his myspace blog for us to solve. I'm not a math guy but its nice to know the answer so a little help would be great.
here it is
Assume x is an integer with many, many digits. In fact, just assume it has a googol digits. What is the minimum number of digits you need to know from x to determine if it is divisible by:
17?
40?
128?
3125?
good luck