How many of the following numbers are prime 11 111 1111 1111

How many of the following numbers are prime?

11

111

1,111

111,111

11,111,111

a. 1

b. 2

c. 4

d. 5

Solution

Answer is option a. 1

The factors of 111 are 1,3,37,111,

The Prime Factors of 1111 are: 1, 11, 101, 1111.

The Prime Factors of 111111: 3 , 7 , 11 , 13 , 37

The Prime Factors of 11111111: 11,1111,11111111 etc