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Abundant Numbers
3rdAbundant Numbers (Long)
3rdCatalan Numbers
1stChristmas Trees
6thDivisors
1stEmirp Numbers
12th
2ndEvil Numbers
1stHappy Numbers
10thLeap Years
16thNiven Numbers
8thNiven Numbers (Long)
4thOdious Numbers
1stPernicious Numbers
1stPrime Numbers
1stPrime Numbers (Long)
1stQuine
1st