1391 — the year and the number: history, mathematics, and significance

Overview of 1391 as a calendar year in the late Middle Ages and as the integer 1391, covering major historical context, the 1391 Iberian anti-Jewish riots, and basic mathematical properties.

Overview

1391 refers both to the calendar year in the late 14th century and to the integer 1391. As a year it lies in the late medieval period, a time of political realignment, recurring warfare, demographic recovery after the Black Death, and increased social tension across Europe and the Mediterranean. As a number it is an odd composite integer whose basic arithmetic properties are straightforward but of interest in elementary number theory.

1391 as a number

The integer 1391 is composite: its prime factorization is 13 × 107, so it is a semiprime (the product of two prime numbers). Its positive divisors are 1, 13, 107 and 1391. It is not a perfect power. In Roman numerals it is written MCCCXCI. In common positional systems its hexadecimal representation is 56F and its binary form is 10101101111. Such representations are routine descriptors used in recreational mathematics and basic arithmetic classification.

Year 1391 — events and trends

The year 1391 is most often remembered for a wave of anti-Jewish violence that began in Seville and spread through parts of Castile and Aragon. Contemporary chronicles and later scholarship describe killings, attacks on property and numerous forced conversions; many Jews became converts (conversos) or fled. These events reshaped urban communities and had long-term legal and social consequences in Iberia, contributing to communal tensions addressed in later centuries.

Iberian Peninsula: The disturbances that began in 1391 are regarded by historians as pivotal in the history of medieval Spanish Jewry because of their scale and aftermath.
Broader context: Elsewhere in Europe and the Mediterranean the period saw localized conflict, dynastic disputes, and the pressure of expanding powers at the margins, such as the Ottomans in the Balkans and Timurid movements in Central Asia; these broader forces shaped political opportunities and vulnerabilities.

Significance and scholarship

Studies of 1391 emphasize how economic stress, popular agitation and clerical rhetoric could combine to produce urban violence. The conversions and migrations that followed had legal, religious and cultural effects that reverberated for generations and are explored through municipal records, notarial documents and narrative sources. When the number 1391 is mentioned the distinction between the arithmetical integer and the historical year is important: the mathematical identity is simple and uncontroversial, while the historical year invites interpretation and regional study.