1091
1091 is a year in the 11th century. The Norman conquest of Sicily was completed with the fall of Noto (Sicily).
- Odd
- Prime
Where 1091 fits
Why 1091 is special
1091 has a profile because of what happened in it rather than because of any property of the number: the Norman conquest of Sicily was completed with the fall of Noto (Sicily).
1091 is part of
Factors & digit properties
- Divisors (2)
- 1, 1091
- Prime factorisation
- 1091
- Digit sum
- 11
- Digital root
- 2
Representations
- Decimal
- 1091
- Scientific notation
- 1.091 × 10^3
Roman numerals
M X C I
MXCI uses the subtractive pair XC: ten before a hundred — a hundred minus ten.
Binary
1 0 0 0 1 0 0 0 0 1 1
1 × 1,024 + 0 × 512 + 0 × 256 + 0 × 128 + 1 × 64 + 0 × 32 + 0 × 16 + 0 × 8 + 0 × 4 + 1 × 2 + 1 × 1 = 1,091
Octal
2 1 0 3
2 × 512 + 1 × 64 + 0 × 8 + 3 × 1 = 1,091
Hexadecimal
4 4 3
4 × 256 + 4 × 16 + 3 × 1 = 1,091
Read as powers of two: 1,024 + 64 + 2 + 1 = 1,091.
In historical numeral systems
Egyptian
1 lotus, 9 hobbles, 1 stroke
1 × 1,000 + 9 × 10 + 1 × 1 = 1,091. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
1 corner wedge + 8 vertical wedges (sixties place), 1 corner wedge + 1 vertical wedge (units place)
18 × 60 + 11 = 1091. Places are separated by a space on the tablet, with the higher place written first.
Systems that simply cannot reach this value are left out. Where a script needs a font most readers do not have, the reading is given instead of the glyphs — see number systems for each system in full.
Other mathematical patterns
- Deficient number
- Twin prime
Related numbers & connections
1091 is a year in the 11th century, in the 1090s.
Numbers Around Us
- appears inHistorical years
why?
Strength 0.50, confidence "high".
History
In 1091, the Norman conquest of Sicily was completed with the fall of Noto (Sicily).
DocumentedHistoryGeography: SicilyPeriod: 1091
Common questions
Is 1091 a prime number?
Yes, 1091 is prime — it has exactly two positive divisors: 1 and itself.
What are the factors of 1091?
The factors of 1091 are 1, 1091.
What is 1091 in Roman numerals?
1091 in Roman numerals is MXCI. XC is subtractive: ten before a hundred — a hundred minus ten. Written additively it would be MLXXXXI, which Roman inscriptions used freely — the strict subtractive form is a later convention.
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: 15 July 2026