John was relieved when the doorbell rang. It meant that the pizza he’d ordered had finally arrived. He quickly paid the delivery driver, and rushed into the kitchen with the pizza box. He flipped open the box and, laying on top of the pizza was a sheet of paper with a list of numbers:

3263
5773
685
8843
2497
16259
16013
14701
10147
8843
2629

But, after looking at the numbers, he realized that those couldn’t be prices. Who ever heard of a pizza costing $162.59?

John then noticed that, scrawled on the inside top of the box the phrase “Prime Tractor”. He thought this was quite weird. Why would some farmer have made a note inside his pizza box about priming a tractor. Then, he realized that an errant black olive was overlaying the first letter of the second word, and that the phrase was really “Prime Factor”.

This still didn’t make much sense. It was only after he finished eating the pizza that he saw the final clue on the bottom of the box, under where the pizza had been “A=2, B=3, C=5, D=7, E=11..”