Question 4871
First find the {{{sqrt (191) }}} and find that it is a number between 13 and 14, since {{{13^2 = 169}}} and {{{13^2 = 196}}}.  


Now you must divide 191 by each prime number up to and including 14, and show that 191 is NOT divisible by any of those numbers.  Since 191 is NOT divisible by 2, 3, 5, 7, 11, or 13, this is a prime number.


R^2 at SCC