1111

1111 is the natural number that follows 1110 and precedes 1112. In base-10 it is a four-digit repdigit and a palindrome. Its prime factorization is 11 × 101, making it a semiprime. In common numeral systems it is written as 1111 in decimal, 10001010111 in binary, 2127 in octal, 0x457 in hexadecimal, and MCXI in Roman numerals.

1111 is square-free, since it is the product of two distinct primes. It has exactly four positive divisors: 1, 11, 101, and 1111. It is a palindromic number in base 10, and the sum of its digits is 4, giving a digital root of 4. In mathematical contexts, it is often cited as a simple example of a semiprime.

Historically, the year 1111 AD falls in the 12th century during the High Middle Ages. The period featured diverse developments across Europe and Asia, with contemporary political and cultural contexts in regions such as the Holy Roman Empire and the Song dynasty.

In popular culture and numerology, the sequence 1111 is sometimes used to evoke ideas of symmetry or scientific curiosity. As a mathematical object, however, it is primarily recognized for its factorization, palindromic form, and representations across numeral systems.