1842
1842 is the year the Treaty of Nanking ceded Hong Kong to Britain.
- Even
- Composite
Where 1842 fits
Why 1842 is special
It ended the First Opium War, fought to force China to accept opium imports. The treaty is the first of what Chinese historiography calls the unequal treaties.
Same number, different meanings
How 1842 is understood across different contexts — never implying one meaning because of another.
- Mathematics
It ended the First Opium War, fought to force China to accept opium imports. The treaty is the first of what Chinese historiography calls the unequal treaties.
- Science
In 1842, Christian Doppler described the effect that bears his name (Austria).
- Law & regulation
The Treaty of Nanking ended a war Britain fought to compel China to permit opium imports, and transferred Hong Kong. The framing of the nineteenth century in Chinese national history begins here.
1842 is part of
Factors & digit properties
- Divisors (8)
- 1, 2, 3, 6, 307, 614, 921, 1842
- Prime factorisation
- 2 × 3 × 307
- Digit sum
- 15
- Digital root
- 6
Representations
- Decimal
- 1842
- Scientific notation
- 1.842 × 10^3
Roman numerals
M D C C C X L I I
MDCCCXLII uses the subtractive pair XL: ten before fifty — fifty minus ten.
Binary
1 1 1 0 0 1 1 0 0 1 0
1 × 1,024 + 1 × 512 + 1 × 256 + 0 × 128 + 0 × 64 + 1 × 32 + 1 × 16 + 0 × 8 + 0 × 4 + 1 × 2 + 0 × 1 = 1,842
Octal
3 4 6 2
3 × 512 + 4 × 64 + 6 × 8 + 2 × 1 = 1,842
Hexadecimal
7 3 2
7 × 256 + 3 × 16 + 2 × 1 = 1,842
Read as powers of two: 1,024 + 512 + 256 + 32 + 16 + 2 = 1,842.
In historical numeral systems
Egyptian
1 lotus, 8 coils of rope, 4 hobbles, 2 strokes
1 × 1,000 + 8 × 100 + 4 × 10 + 2 × 1 = 1,842. 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), 4 corner wedges + 2 vertical wedges (units place)
30 × 60 + 42 = 1842. 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
- Abundant number
Related numbers & connections
1842 is a year in the 19th century, in the 1840s.
The Treaty of Nanking ceded Hong Kong in 1842 and it was returned in 1997, 155 years later under a framework promising a distinct system for fifty more.
View 1997 →Numbers Around Us
- appears inHistorical years
why?
Strength 0.50, confidence "high".
Other connections
- developed from1997
why?
Strength 0.50, confidence "high".
Science
In 1842, Christian Doppler described the effect that bears his name (Austria).
DocumentedScienceGeography: AustriaPeriod: 1842
Law & regulation
The Treaty of Nanking ended a war Britain fought to compel China to permit opium imports, and transferred Hong Kong. The framing of the nineteenth century in Chinese national history begins here.
DocumentedLaw & regulationGeography: China and BritainPeriod: 1842
Common questions
Is 1842 a prime number?
No, 1842 is not prime.
What are the factors of 1842?
The factors of 1842 are 1, 2, 3, 6, 307, 614, 921, 1842.
What is 1842 in Roman numerals?
1842 in Roman numerals is MDCCCXLII. XL is subtractive: ten before fifty — fifty minus ten. Written additively it would be MDCCCXXXXII, 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: 2 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 15 July 2026