Question

Prove that 111111..…..1 (91 digits) is not a prime number.

Answer 1

A divisible by B means that A/B =integer
ex:24 divisible by 6 as 24/6=4 an integer

here
111111(6 times ) divisible by 111(3times) and 11(2 times).......[6=3*2]
1111.....(10 times ) divisible by 11111(5 times ) and 11(2 times).....[10=5*2]


like this
1111...(91 times) divisible by 11111..(13 times) and 1111...(7 times) ......[91=13*7]