Related Clues:

• Finger, e.g.
• Inclusion in safer passwords
• X, e.g.
• 2, for one
• 1 in 1,000,000?
• One of 101 in a googol
• Zip code component
• Sudoku fill-in
• 1, 2, 3, for instance
• Affable and sociable
• 1, 2, 3, say
• Symbol for number
• Diagram or digit
• The written symbol of a number
• Written symbol of a number