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 connects to:
- historical years — appears in
- 1930 — contrasts with
Same number, different meanings
How 1801 is understood across different contexts — never implying one meaning because of another.
- Mathematics
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.
- History
In 1801, the Acts of Union created the United Kingdom of Great Britain and Ireland (Britain and Ireland).
- 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.
1801 is part of
Factors & digit properties
- Divisors (2)
- 1, 1801
- Prime factorisation
- 1801
- Digit sum
- 10
- Digital root
- 1
Representations
- Decimal
- 1801
- Scientific notation
- 1.801 × 10^3
Roman numerals
M D C C C I
Binary
1 1 1 0 0 0 0 1 0 0 1
1 × 1,024 + 1 × 512 + 1 × 256 + 0 × 128 + 0 × 64 + 0 × 32 + 0 × 16 + 1 × 8 + 0 × 4 + 0 × 2 + 1 × 1 = 1,801
Octal
3 4 1 1
3 × 512 + 4 × 64 + 1 × 8 + 1 × 1 = 1,801
Hexadecimal
7 0 9
7 × 256 + 0 × 16 + 9 × 1 = 1,801
Read as powers of two: 1,024 + 512 + 256 + 8 + 1 = 1,801.
In historical numeral systems
Egyptian
1 lotus, 8 coils of rope, 1 stroke
1 × 1,000 + 8 × 100 + 1 × 1 = 1,801. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
3 corner wedges (sixties place), 1 vertical wedge (units place)
30 × 60 + 1 = 1801. 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
1801 is a year in the 19th century, in the 1800s.
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 →Numbers Around Us
- appears inHistorical years
why?
Strength 0.50, confidence "high".
Other connections
- contrasts with1930
why?
Strength 0.50, confidence "high".
History
In 1801, the Acts of Union created the United Kingdom of Great Britain and Ireland (Britain and Ireland).
DocumentedHistoryGeography: Britain and IrelandPeriod: 1801
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: 2 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 15 July 2026