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.
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
- Binary
- 10001010001
- Octal
- 2121
- Hexadecimal
- 451
- Roman numeral
- MCV
- Scientific notation
- 1.105 × 10^3
Other mathematical patterns
- Deficient number
- Lucky number (mathematical sieve)
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: 1 reviewer-confirmed record, sourced and reviewed before publication.
Last reviewed: 3 August 2026