1105
1,105 is the second Carmichael number.
- Odd
- Composite
Where 1105 fits
Why 1105 is special
Like 561 it is composite and passes Fermat's primality test for every base. It is also the smallest number expressible as a sum of two squares in four different ways.
1105 is part of
Factors & digit properties
- Divisors (8)
- 1, 5, 13, 17, 65, 85, 221, 1105
- Prime factorisation
- 5 × 13 × 17
- Digit sum
- 7
- Digital root
- 7
Representations
- Decimal
- 1105
- Scientific notation
- 1.105 × 10^3
Roman numerals
M C V
Binary
1 0 0 0 1 0 1 0 0 0 1
1 × 1,024 + 0 × 512 + 0 × 256 + 0 × 128 + 1 × 64 + 0 × 32 + 1 × 16 + 0 × 8 + 0 × 4 + 0 × 2 + 1 × 1 = 1,105
Octal
2 1 2 1
2 × 512 + 1 × 64 + 2 × 8 + 1 × 1 = 1,105
Hexadecimal
4 5 1
4 × 256 + 5 × 16 + 1 × 1 = 1,105
Read as powers of two: 1,024 + 64 + 16 + 1 = 1,105.
In historical numeral systems
Egyptian
1 lotus, 1 coil of rope, 5 strokes
1 × 1,000 + 1 × 100 + 5 × 1 = 1,105. 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), 2 corner wedges + 5 vertical wedges (units place)
18 × 60 + 25 = 1105. 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
- Lucky number (mathematical sieve)
Related numbers & connections
1105 is a year in the 12th century, in the 1100s.
Numbers Around Us
- appears inHistorical years
why?
Strength 0.50, confidence "high".
History
In 1105, Henry IV was forced to abdicate by his son (Central Europe).
DocumentedHistoryGeography: Central EuropePeriod: 1105
Mathematics
1,105 is the second Carmichael number and separately the smallest number that is a sum of two squares in four distinct ways. Numbers of moderate size often carry several unrelated distinctions.
DocumentedMathematics
Common questions
Is 1105 a prime number?
No, 1105 is not prime.
What are the factors of 1105?
The factors of 1105 are 1, 5, 13, 17, 65, 85, 221, 1105.
What is 1105 in Roman numerals?
1105 in Roman numerals is MCV.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 2 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 15 July 2026