The seventeenth of the primes.
Its twin is twentynine.
Add seven triangular.
It named the Valley.
This riddle is taken from https://www.nevercompletedgame.com/ It is the final question of the challenge (number 41), and it has not been solved yet. My guess so far is that each line refers to a two-digit number, and that the numbers form some kind of a cipher, since my guesses contain some repeated numbers. My guesses for the numbers on each line:
- 59 (the seventeenth prime number)
- 31 (29's twin prime)
- 84 (atomic number of Polonium)
- 16 (first word in the song "Let's Drive" by John Oates)
- 89 (year that Raúl Alfonsín left office)
- 84 (sum of the first seven triangular numbers)
- 16 (sweet sixteen)
- 14 (atomic number of Silicon)
I have tried using a number to letter online decoder and a base 26 decoder, but I wasn't able to get anything meaningful with these numbers. I'm not 100% positive on any of them really, I might be completely off with my entire approach. The answers and explanations for the first 40 on this website are given here, for those that want to skip to 41 and test their solutions for this riddle: