1666
1666 is the year of the Great Fire of London.
- Even
- Composite
Where 1666 fits
Why 1666 is special
The fire destroyed some 13,200 houses and most of the medieval city in four days, with a recorded death toll in single figures that historians consider a substantial undercount. It also ended the plague outbreak of the previous year, though the connection is more often asserted than demonstrated.
1666 is part of
Factors & digit properties
- Divisors (12)
- 1, 2, 7, 14, 17, 34, 49, 98, 119, 238, 833, 1666
- Prime factorisation
- 2 × 7^2 × 17
- Digit sum
- 19
- Digital root
- 1
Representations
- Decimal
- 1666
- Binary
- 11010000010
- Octal
- 3202
- Hexadecimal
- 682
- Roman numeral
- MDCLXVI
- Scientific notation
- 1.666 × 10^3
Other mathematical patterns
- Deficient number
- Happy number
Related numbers & connections
The Great Fire followed London's plague year directly, and the claim that it ended the outbreak is repeated far more often than it is demonstrated.
View 1665 →The Great Fire of 1666 and the Great Storm of 1703 were both London catastrophes, and Defoe's account of the second assembled eyewitness reports into recognisably modern journalism.
View 1703 →History
The Great Fire destroyed around 13,200 houses and most of the medieval City of London in four days, with an official death toll in single figures that historians treat as a substantial undercount of the poor and unrecorded. The claim that it ended the previous year's plague is asserted more often than it is demonstrated.
DocumentedHistoryGeography: London, EnglandPeriod: 1666
Common questions
Is 1666 a prime number?
No, 1666 is not prime.
What are the factors of 1666?
The factors of 1666 are 1, 2, 7, 14, 17, 34, 49, 98, 119, 238, 833, 1666.
What is 1666 in Roman numerals?
1666 in Roman numerals is MDCLXVI.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 1 reviewer-confirmed record, sourced and reviewed before publication.
Last reviewed: 3 August 2026