21

from the GNU version of the Collaborative International Dictionary of English.

• adjective one more than twenty; twenty plus one more; denoting a quantity consisting of twenty-one items or units; -- representing the number twenty-one as Arabic numerals.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The cardinal number twenty-one.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the cardinal number that is the sum of twenty and one
• adjective being one more than twenty