According to Wolfram Alpha, it's not a triangular number. 
http://www.wolframalpha.com/input/?i=is+2147129+a+triangular+number%3F
EDIT: also, more info from OP
Edit2: First post changed again
http://www.wolframalpha.com/input/?i=is+2147129+a+triangular+number%3F
EDIT: also, more info from OP
Edit2: First post changed again
Quote from: OP
*Hint for "Onion.7z":
- Match the implied platonic solids to their designated elements in the correct order.
- Always apply Bitcoin protocol - "Bitcoin hash is the hash of the hash, so two SHA256 rounds are needed"
-File "onion" or file "again," choose a path. Is one in the future, is one in the past?
- File "onion" or file "again," choose a path. Which one leads to bitcoin?
- Match the implied platonic solids to their designated elements in the correct order.
- Always apply Bitcoin protocol - "Bitcoin hash is the hash of the hash, so two SHA256 rounds are needed"
-
- File "onion" or file "again," choose a path. Which one leads to bitcoin?