What is the greatest prime factor of 4^16 - 2^30?  Choose the correct choice
A) 2
B) 3
C) 5
D) 7
E) 11
4^16 - 2^30   =(2^2)^16 - 2^30   = 2^32 - 2^30   = 2^30 (2^2 -1)   = 2^30 * (4-1)   = 2^30 * 3   The greatest prime factor is 3.   The answer is 3.
<result>B</result>
What is the greatest prime factor of 4^16 - 2^30?