XXI

from WordNet (r) 3.0 (2006)

xxi
    adj 1: being one more than twenty [syn: {twenty-one}, {21},
           {xxi}]
    n 1: the cardinal number that is the sum of twenty and one [syn:
         {twenty-one}, {21}, {XXI}]

from The Collaborative International Dictionary of English v.0.48

xxi \xxi\, adj.
   The Roman number representing {twenty-one}.

   Syn: twenty-one, 21.
        [WordNet 1.5]

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