Related Clues:

• ___ duck
• Like any number ending in five
• Kind of job or lot
• Match-less?
• Without a match
• Like 7 or 11
• Offbeat
• Unmatched, like socks
• Lacking a partner
• Unmatched, as a sock
• Matchless, e.g.
• Unlike 666
• Like all but one prime
• Prompting a 'hmm,' perhaps
• Like all prime numbers except 2