The correct option is (B): 4. We will try to find a pattern in the last three digits of the given number. Last three digits of: 10051 = 005 10052 = 025 10053 = 125 10054 = 625 10055 = 125 10056 = 625 Now, this pattern will repeat. From the above pattern, we can say that the last three digits of 10051001 will be 125. Now, 125 = 33 Thus, the number of factors = 3 + 1 = 4.