What is the greatest prime factor of 1+2+3+。。。

What is the greatest prime factor of 1+2+3+。。。+22?

Quiz

Answer/Solution

23

Steps/Work

find the sum from direct formula = n(n+1)/2 = 22(22+1)/2 = 11*23...
23 is a PRIME number, so ans is 23..
C is the answer