Overview
1291 can refer to the integer 1291 or to the year AD 1291 in the late 13th century. As a number it has elementary arithmetic properties of interest to students of numeracy; as a year it is remembered for events that have entered broad historical narratives, notably the fall of the Crusader port of Acre and a charter associated with the early Swiss Confederacy.
Mathematical properties
In arithmetic, 1291 is an odd four‑digit integer and a prime number, meaning its only positive divisors are 1 and itself. Its decimal digits sum to 13, so it is not divisible by 3. In binary it is written as 101000001011, in hexadecimal as 0x50B and in octal as 2413. These features place it among ordinary but well‑defined objects in elementary number theory.
Fall of Acre (AD 1291)
The capture of Acre in 1291 by the Mamluk forces is widely cited as the effective end of the Crusader presence on the Levantine mainland. After a siege, Mamluk troops overcame the city's defenses and many surviving Latin inhabitants and military orders evacuated to nearby islands and to Cyprus. The loss of Acre closed the last major continental stronghold held by Western crusaders and marked a turning point in Mediterranean politics and trade patterns.
Federal Charter and Swiss tradition
A document dated to 1291, commonly called the Federal Charter, records an alliance among the alpine communities of Uri, Schwyz and Unterwalden. In Swiss historiography and public memory the charter is regarded as an early foundation for the Old Swiss Confederacy; it has been celebrated symbolically and is associated with the Swiss national day celebrated on August 1. The charter itself survives as an archival document that later generations treated as central to national origin narratives.
Aftermath and significance
Both the fall of Acre and the 1291 charter have long legacies. The fall of Acre led to a reshaping of power along the eastern Mediterranean coast and signalled the end of major crusading efforts to hold territory in the Holy Land; many Western military orders relocated and European attention increasingly turned to maritime trade and other theatres. The Federal Charter became a touchstone for evolving Swiss institutions and identity, cited in later medieval and early modern developments that produced the modern Swiss state.
Notes on chronology and usage
As a chronological marker, 1291 sits near the close of the 13th century, a period of political, military and social change across Europe and the Near East. As a number, 1291 is one entry among the infinite sequence of primes and is sometimes encountered in lists of prime years or in simple recreational mathematics.