1845
1845 is the year the Great Famine began in Ireland.
- Odd
- Composite
Where 1845 fits
Why 1845 is special
Potato blight destroyed the crop, and about a million people died while Ireland continued exporting food under armed guard. The population fell by roughly a quarter through death and emigration, and has never returned to its pre-famine level.
Same number, different meanings
How 1845 is understood across different contexts — never implying one meaning because of another.
- Mathematics
Potato blight destroyed the crop, and about a million people died while Ireland continued exporting food under armed guard. The population fell by roughly a quarter through death and emigration, and has never returned to its pre-famine level.
- History
In 1845, potato blight triggered the Great Famine in Ireland (Ireland).
- Science
In 1845, John Couch Adams calculated where an unseen planet must be from irregularities in Uranus's orbit, and Neptune was found close to the predicted position the following year (England and France).
1845 is part of
Factors & digit properties
- Divisors (12)
- 1, 3, 5, 9, 15, 41, 45, 123, 205, 369, 615, 1845
- Prime factorisation
- 3^2 × 5 × 41
- Digit sum
- 18
- Digital root
- 9
Representations
- Decimal
- 1845
- Scientific notation
- 1.845 × 10^3
Roman numerals
M D C C C X L V
MDCCCXLV uses the subtractive pair XL: ten before fifty — fifty minus ten.
Binary
1 1 1 0 0 1 1 0 1 0 1
1 × 1,024 + 1 × 512 + 1 × 256 + 0 × 128 + 0 × 64 + 1 × 32 + 1 × 16 + 0 × 8 + 1 × 4 + 0 × 2 + 1 × 1 = 1,845
Octal
3 4 6 5
3 × 512 + 4 × 64 + 6 × 8 + 5 × 1 = 1,845
Hexadecimal
7 3 5
7 × 256 + 3 × 16 + 5 × 1 = 1,845
Read as powers of two: 1,024 + 512 + 256 + 32 + 16 + 4 + 1 = 1,845.
In historical numeral systems
Egyptian
1 lotus, 8 coils of rope, 4 hobbles, 5 strokes
1 × 1,000 + 8 × 100 + 4 × 10 + 5 × 1 = 1,845. 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 + 5 vertical wedges (units place)
30 × 60 + 45 = 1845. 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
Related numbers & connections
1845 is a year in the 19th century, in the 1840s.
The Bengal famine of 1943 and the Irish famine from 1845 both occurred under British administration with food being exported during the deaths. Responsibility in both cases remains actively contested.
View 1943 →History
In 1845, potato blight triggered the Great Famine in Ireland (Ireland).
DocumentedHistoryGeography: IrelandPeriod: 1845Potato blight destroyed the crop from 1845 and about a million people died while Ireland continued to export food under armed guard. Death and emigration cut the population by roughly a quarter, and it has never returned to its pre-famine level.
DocumentedHistoryGeography: IrelandPeriod: 1845–1852
Science
In 1845, John Couch Adams calculated where an unseen planet must be from irregularities in Uranus's orbit, and Neptune was found close to the predicted position the following year (England and France).
DocumentedScienceGeography: England and FrancePeriod: 1845
Common questions
Is 1845 a prime number?
No, 1845 is not prime.
What are the factors of 1845?
The factors of 1845 are 1, 3, 5, 9, 15, 41, 45, 123, 205, 369, 615, 1845.
What is 1845 in Roman numerals?
1845 in Roman numerals is MDCCCXLV. XL is subtractive: ten before fifty — fifty minus ten. Written additively it would be MDCCCXXXXV, 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: 3 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 15 July 2026