So my last riddle turned out to be too easy. Lets see if this one is difficult enough.

You wake up with a huge headache and look around you. Somehow you managed to end up in a white room of about 2 by 2 meters with no furniture or windows. The only thing that stands out is a white door with a small computer screen next to it. You try opening the door but its locked. It doesn't seem like it can be forced either. On the computer screen you see that the door is locked with a six-digit numeric passcode. Fortunately whoever set the passcode put a hint with it, probably because they aren't clever enough to remember the passcode themselves. The hint reads:

2351389233159728657, I shall unite with my former self, but once united I cannot be split. Tell me, what will I be next?

Which code do you enter to open the door?


1 Answer 1


The numeric code is 514229.

The numbers in the string are 2, 3, 5, 13, 89, 233, 1597, 28657, which are all prime Fibonacci numbers. The next one is 514229.

The clue "I shall unite with my former self" refers to the fact that each number is the sum of the previous two numbers, and the clue "but once united I cannot be split" refers to the fact that the numbers cannot be divided.

  • 4
    $\begingroup$ People on this website are too clever :< $\endgroup$
    – Poelie
    Apr 16, 2015 at 21:51
  • $\begingroup$ It comes with the territory. :) $\endgroup$
    – user88
    Apr 16, 2015 at 21:57

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