Every digit of a number written in binary is either 0 or 1. To translate a number from binary, multiply the nth digit (reading from right to left) by 2^(n-1)
What is the largest prime number (written in binary) that is a factor of both 10010000 and 100100000 ?
Choose the correct choice from the following choices:
A) 10
B) 11
C) 1001
D) 1011
E) 10001

Rationale: binary divison can provide a quick answer if you are comfortable with it . as option e is the biggest binary number we try with it first : 100010000 / 1001 = 10000 1000100000 / 1001 = 100000 so answer is option is c
Answer: C