Friday 16 June 2017 — This is more than seven years old. Be careful.
55 is in the Fibonacci sequence:
1 1 2 3 5 8 13 21 34 55 ...
55 is a triangular number:
1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 = 55
It is the largest number that is both Fibonacci and triangular.
It is also a Kaprekar number:
55² = 3025 and 30+25 = 55
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