19 isn't a factor of 68 and 34 isn't prime. Other than that... The largest prime factor of 68 is 17.
17
68 34,2 17,2,2
The largest prime factor of 92 is 23.
The largest prime factor of 1,505 is 43.
The largest prime factor of 93,093 is 31.
The largest prime factor of 38 is 19.
The largest prime factor of 42 is 7
The largest prime factor of 4,110 is 137.
The largest prime factor of 8,091 is: 31
The largest prime factor of 1,996 is 499.
The largest prime factor of 358 is 179.