1801
1801 is the year of the first British census and the first asteroid discovery.
- Odd
- Prime
Where 1801 fits
Why 1801 is special
Ceres was found on the first night of the century and was initially classified as a planet, then as an asteroid, and is now a dwarf planet. Its category has changed three times without the object changing at all.
1801 is part of
Factors & digit properties
- Divisors (2)
- 1, 1801
- Prime factorisation
- 1801
- Digit sum
- 10
- Digital root
- 1
Representations
- Decimal
- 1801
- Binary
- 11100001001
- Octal
- 3411
- Hexadecimal
- 709
- Roman numeral
- MDCCCI
- Scientific notation
- 1.801 × 10^3
Other mathematical patterns
- Deficient number
- Lucky number (mathematical sieve)
Related numbers & connections
Ceres was found in 1801 and called a planet, then an asteroid, then a dwarf planet; Pluto was found in 1930 and reclassified in 2006. Neither object changed.
View 1930 →Other connections
- contrasts with1930
why?
Strength 0.50, confidence "high".
Science
Ceres was called a planet, then an asteroid, then a dwarf planet. Nothing about the object changed; the categories did, which is a useful corrective to treating classification as a property of nature rather than of us.
DocumentedSciencePeriod: 1801
Common questions
Is 1801 a prime number?
Yes, 1801 is prime — it has exactly two positive divisors: 1 and itself.
What are the factors of 1801?
The factors of 1801 are 1, 1801.
What is 1801 in Roman numerals?
1801 in Roman numerals is MDCCCI.
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