1980
1980 is the year smallpox was declared eradicated.
- Even
- Composite
Where 1980 fits
Why 1980 is special
It is the only human disease ever eliminated, after a campaign built on ring vaccination rather than vaccinating everyone. The last natural case was in Somalia in 1977; the last death was a laboratory accident in Birmingham in 1978.
Same number, different meanings
How 1980 is understood across different contexts — never implying one meaning because of another.
- Mathematics
It is the only human disease ever eliminated, after a campaign built on ring vaccination rather than vaccinating everyone. The last natural case was in Somalia in 1977; the last death was a laboratory accident in Birmingham in 1978.
- History
In 1980, smallpox was declared eradicated by the World Health Organization.
- Science
Smallpox is the sole human disease eradicated, achieved by ring vaccination around outbreaks rather than vaccinating everyone. The last natural case was in Somalia in 1977; the last death was a British laboratory accident in 1978.
1980 is part of
Factors & digit properties
- Divisors (36)
- 1, 2, 3, 4, 5, 6, 9, 10, 11, 12, 15, 18, 20, 22, 30, 33, 36, 44, 45, 55, 60, 66, 90, 99, 110, 132, 165, 180, 198, 220, 330, 396, 495, 660, 990, 1980
- Prime factorisation
- 2^2 × 3^2 × 5 × 11
- Digit sum
- 18
- Digital root
- 9
Representations
- Decimal
- 1980
- Scientific notation
- 1.980 × 10^3
Roman numerals
M C M L X X X
MCMLXXX uses the subtractive pair CM: a hundred before a thousand — a thousand minus a hundred.
Binary
1 1 1 1 0 1 1 1 1 0 0
1 × 1,024 + 1 × 512 + 1 × 256 + 1 × 128 + 0 × 64 + 1 × 32 + 1 × 16 + 1 × 8 + 1 × 4 + 0 × 2 + 0 × 1 = 1,980
Octal
3 6 7 4
3 × 512 + 6 × 64 + 7 × 8 + 4 × 1 = 1,980
Hexadecimal
7 b c
7 × 256 + b × 16 + c × 1 = 1,980
Read as powers of two: 1,024 + 512 + 256 + 128 + 32 + 16 + 8 + 4 = 1,980.
In historical numeral systems
Egyptian
1 lotus, 9 coils of rope, 8 hobbles
1 × 1,000 + 9 × 100 + 8 × 10 = 1,980. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
3 corner wedges + 3 vertical wedges (sixties place), empty units place
33 × 60 + 0 = 1980. Places are separated by a space on the tablet, with the higher place written first. The second place is empty, and this is precisely the case the early system could not write unambiguously — the same wedges alone would also read as 1.
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
- Harshad (Niven) number
Related numbers & connections
1980 is a year in the 20th century, in the 1980s.
Smallpox was declared eradicated in 1980, 184 years after Jenner's vaccination experiment. It remains the only human disease eliminated.
View 1796 →History
In 1980, smallpox was declared eradicated by the World Health Organization.
DocumentedHistoryGeography: globalPeriod: 1980
Science
Smallpox is the sole human disease eradicated, achieved by ring vaccination around outbreaks rather than vaccinating everyone. The last natural case was in Somalia in 1977; the last death was a British laboratory accident in 1978.
DocumentedSciencePeriod: 1980
Common questions
Is 1980 a prime number?
No, 1980 is not prime.
What are the factors of 1980?
The factors of 1980 are 1, 2, 3, 4, 5, 6, 9, 10, 11, 12, 15, 18, 20, 22, 30, 33, 36, 44, 45, 55, 60, 66, 90, 99, 110, 132, 165, 180, 198, 220, 330, 396, 495, 660, 990, 1980.
What is 1980 in Roman numerals?
1980 in Roman numerals is MCMLXXX. CM is subtractive: a hundred before a thousand — a thousand minus a hundred. Written additively it would be MDCCCCLXXX, 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