There is no last prime number: they go on for ever. The first prime larger than 100 is 101.
The last prime number from 1 to 100 is 97, and the first is 2. 97+2 = 99
The last prime number before 100 is 97
The sum of 2 and 97 is 99.
The first prime number that is less than 100 would be "97".
97
97
106
1060
It is: 101
101
102