The next day I called the National Defense Telecommunications Research and Development Division – now I know the correct division, but at first I was bounced around between operators, each one more interested in getting away for a coffee break. It was easier to find the prime number than to get that damn phone number and schedule a meeting!

I took the USB stick containing our number and drove to a nondescript center some distance from the city. I passed vast irrigation furrows, where the grass was marked with strange metal studs. Soon I reached a checkpoint, where they collared me, and demanded my ID.

Eventually I approached a building with plate-glass windows, overlooking the security guards patrolling outside. I found myself in a room that was almost empty, just a desk and two chairs.

An old man carrying an unbranded laptop entered the room. He greeted me, took the memory stick, and nodded for me to sit. This was very different to the drops I did for MegaPrimes.

He told me, with a kind of joyous meticulousness: "You have a very interesting prime number. I don't think anyone knows it... I'm certainly not familiar with its leading digits, and it's quite short too. We'll purchase it under the standard agreement, which we sign with all of our discoverers.

"I look forward to our future collaboration. I should also note that from now on we shall only purchase from you nontrivial prime numbers of at least 150 digits."

He looked at me over his glasses to see if I minded. Of course, I didn't totally understand what he was saying, but I don't think he could tell. I asked for more information about the terms of the agreement, and he slid some papers over the desk. I gave them a scan as he continued: "We require a week to verify if your number is indeed a prime. Then, if your number is not in our databases yet, you'll receive a payment composed of the following amounts:

"A principal of $5,000 as a grant from the Ministry of Research.

"A bonus of $10,000 approved by the Ministry of Defense. A word of warning: this bonus is subject to internal conditions, so it's by no means certain that you'll get it.

"A bonus of $7,000 awarded by the Alliance of Secured Payment Operators. This bonus varies each year, but – good news for you – it tends to increase.

"A bonus of $1,000 provided by the Number Cartography Project. This bonus is optional; it requires that your number be made public when we no longer need it. There is a checkbox in case you want to keep it secret... but I've never seen it checked.

"The entire amount is paid in monthly installments, $1,000 per month. The first payment is made within three months, at the month end. Yes, it's a long time to wait – but since you're being paid by the government, you know you're going to be solvent.

"Oh, and know that if another company finds your prime, or if hackers break the code, then our contract shall become null and void. But you do keep the funds already paid to you.

"Welcome to the club!"