Related Clues:

• Match-less?
• Without a match
• Off the beaten path
• Like 7 or 11
• Strangely wondrous
• Offbeat
• Unmatched, like socks
• Far from humdrum
• Lacking a partner
• Unmatched, as a sock
• Strange and rare
• Matchless, e.g.
• Unlike 666
• Alien
• Like all but one prime