In recreational mathematics, a repdigit is a natural number composed of repeated instances of the same digit, most often in the decimal numeral system.

Examples are 11, 222, 4444, 77777, and 999999. All repdigits are palindromic numbers and are multiples of repunits. One of the most famous repdigits is 666, the number of the beast.

The word repdigit is a portmanteau word, formed from repeated digit.

External link

• Repdigits at MathWorld