1111111111
1111111111 is the decimal numeral consisting of ten consecutive ones. In mathematics it is the tenth repunit in base 10, written as R10, and equals (10^10 − 1)/9, which is 1,111,111,111.
As an even-length repunit, it is divisible by 11. In fact, 1111111111 factors as 11 × 101010101,
If interpreted in binary, the string 1111111111 denotes the value 2^10 − 1, which equals 1023 in
In decimal notation, it provides a simple test pattern for software or hardware that handles large integers.
See also: repunit, Mersenne numbers, bitmask, binary numeral systems.