There is a neat website that factors numbers for you:
http://www.coolmathgames9.com/factors/
It says that the factors of 7983 are: 1, 3, 9, 887, 2661, and 7983.
Of these factors, the only one that is a factor of 100,000 is 1.
So, the greatest common factor of 7983 and 100,000 is 1.