Characteristics
1 is a Fibonacci number
1 is a triangular number
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The next triangular is:
31 is a pentagonal number
1 is a hexagonal number
1 is a heptagonal number
1 is a octogonal number
1 is a palindromic number in decimal system
1 is a palindromic number in binary system (1)
1 is a palindromic number in septimal system (1)