111

111 is the natural number that follows 110 and precedes 112. In decimal notation it is written with three identical digits. It is the third repunit in base 10, equal to (10^3−1)/9, and its prime factorization is 3 × 37. The number is palindromic and divisible by 3, since the sum of its digits is 3. In binary it is 1101111, and in hexadecimal it is 0x6F.

111 is the atomic number of roentgenium, a synthetic superheavy element with symbol Rg. Roentgenium has no stable isotopes and is produced in particle accelerators for scientific research. It is highly radioactive and has very short half-lives, contributing to limited experimental data about its chemical properties.

In computing and text encoding, the decimal value 111 corresponds to the lowercase letter 'o' in ASCII and Unicode (U+006F).

In the United Kingdom, 111 is the non-emergency medical helpline, providing health information and triage outside of urgent-care channels.

Some numerology and popular-culture references treat 111 as a number with symbolic associations, though such meanings are not scientifically defined.