1945
1945 is the year the Second World War ended and the United Nations was founded.
- Odd
- Composite
Where 1945 fits
Why 1945 is special
1945 is where the modern international order starts. Germany surrendered in May, the atomic bombings of Hiroshima and Nagasaki came in August followed by Japan's surrender, and the United Nations Charter was signed in June and took effect in October. The Nuremberg trials began in November, establishing that individuals could be prosecuted for state acts.
Same number, different meanings
How 1945 is understood across different contexts — never implying one meaning because of another.
- Mathematics
1945 is where the modern international order starts. Germany surrendered in May, the atomic bombings of Hiroshima and Nagasaki came in August followed by Japan's surrender, and the United Nations Charter was signed in June and took effect in October. The Nuremberg trials began in November, establishing that individuals could be prosecuted for state acts.
- History
In 1945, the Second World War ended, atomic bombs were used on Hiroshima and Nagasaki, and the United Nations was founded.
- Law & regulation
The Nuremberg trials, opening in November 1945, established that a person could be prosecuted for acts committed on behalf of a state — that following orders was not by itself a defence. Together with the UN Charter signed in June, it is why 1945 marks the start of the modern international legal order rather than merely the end of a war.
1945 is part of
Factors & digit properties
- Divisors (4)
- 1, 5, 389, 1945
- Prime factorisation
- 5 × 389
- Digit sum
- 19
- Digital root
- 1
Representations
- Decimal
- 1945
- Scientific notation
- 1.945 × 10^3
Roman numerals
M C M X L V
MCMXLV uses the subtractive pair XL: ten before fifty — fifty minus ten.
Binary
1 1 1 1 0 0 1 1 0 0 1
1 × 1,024 + 1 × 512 + 1 × 256 + 1 × 128 + 0 × 64 + 0 × 32 + 1 × 16 + 1 × 8 + 0 × 4 + 0 × 2 + 1 × 1 = 1,945
Octal
3 6 3 1
3 × 512 + 6 × 64 + 3 × 8 + 1 × 1 = 1,945
Hexadecimal
7 9 9
7 × 256 + 9 × 16 + 9 × 1 = 1,945
Read as powers of two: 1,024 + 512 + 256 + 128 + 16 + 8 + 1 = 1,945.
In historical numeral systems
Egyptian
1 lotus, 9 coils of rope, 4 hobbles, 5 strokes
1 × 1,000 + 9 × 100 + 4 × 10 + 5 × 1 = 1,945. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
3 corner wedges + 2 vertical wedges (sixties place), 2 corner wedges + 5 vertical wedges (units place)
32 × 60 + 25 = 1945. 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
- Semiprime
- Lucky number (mathematical sieve)
Related numbers & connections
1945 is a year in the 20th century, in the 1940s.
The League of Nations began work in 1920 without the country that proposed it; the United Nations from 1945 was designed around that failure.
View 1920 →Numbers Around Us
History
In 1945, the Second World War ended, atomic bombs were used on Hiroshima and Nagasaki, and the United Nations was founded.
DocumentedHistoryGeography: globalPeriod: 1945The war in Europe ended in May 1945 and in the Pacific in September. The United Nations Charter was signed in June of the same year, so the institutions built to prevent a recurrence date from the months in which the conflict was still ending.
DocumentedHistoryGeography: GlobalPeriod: 1945
Law & regulation
The Nuremberg trials, opening in November 1945, established that a person could be prosecuted for acts committed on behalf of a state — that following orders was not by itself a defence. Together with the UN Charter signed in June, it is why 1945 marks the start of the modern international legal order rather than merely the end of a war.
DocumentedLaw & regulationGeography: Nuremberg, Allied-occupied Germany; the principles adopted internationally thereafterPeriod: 1945
Common questions
Is 1945 a prime number?
No, 1945 is not prime.
What are the factors of 1945?
The factors of 1945 are 1, 5, 389, 1945.
What is 1945 in Roman numerals?
1945 in Roman numerals is MCMXLV. XL is subtractive: ten before fifty — fifty minus ten. Written additively it would be MDCCCCXXXXV, 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