The Collaborative International Dictionary of English v.0.48:

27 \27\ adj.
   1. denoting a quantity consisting of twenty-seven items or
      units; -- representing the number twenty-seven as Arabic
      numerals

   Syn: twenty-seven, xxvii
        [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

27
    adj 1: being seven more than twenty [syn: twenty-seven, 27,
           xxvii]
    n 1: the cardinal number that is the sum of twenty-six and one
         [syn: twenty-seven, 27, XXVII]