What is the greatest prime factor of 8^12 - 2^30?
Select:
A) 2  B) 3  C) 5  D) 7  E) 11
8^12 - 2^30?   8 = 2^3   8^12 = 2^36   2^36 - 2^30 = 2^30 (2^6 - 1) = 2^30 (64 - 1) = 2^30 (63) = 2^30 (7*3*3)   hence 2,3,7 are the prime factors of 8^12 - 2^30. here, 7 is the greatest prime factor.   Option 7 is correct.
<result>D</result>
What is the greatest prime factor of 8^12 - 2^30?