Repdigit

A repdigit is a natural number with all digits the same in a given base (here base 10). Examples: 1, 2, …, 9, 11, 22, 33, …, 99, 111, 222, etc.

Key features

• Single-digit numbers 1–9 are repdigits.
• Often studied in recreational mathematics and puzzles.

Examples:

1, 2, 11, 22, 111, 333, 9999

Further reading

• Repdigit on Wikipedia
• Repdigit on OEIS