1939
1939 is the year the Second World War began in Europe.
- Odd
- Composite
Where 1939 fits
Why 1939 is special
Germany invaded Poland on 1 September and Britain and France declared war two days later. The date marks the European opening specifically: fighting in Asia had been under way since 1937, and dating the war from 1939 is a convention that reflects a European vantage point.
Same number, different meanings
How 1939 is understood across different contexts — never implying one meaning because of another.
- Mathematics
Germany invaded Poland on 1 September and Britain and France declared war two days later. The date marks the European opening specifically: fighting in Asia had been under way since 1937, and dating the war from 1939 is a convention that reflects a European vantage point.
- History
In 1939, the Second World War began with the invasion of Poland.
- Science
In 1939, Lise Meitner and Otto Frisch explained the splitting of the uranium nucleus and named it fission, calculating the energy it would release (Sweden and Denmark).
1939 is part of
Factors & digit properties
- Divisors (4)
- 1, 7, 277, 1939
- Prime factorisation
- 7 × 277
- Digit sum
- 22
- Digital root
- 4
Representations
- Decimal
- 1939
- Scientific notation
- 1.939 × 10^3
Roman numerals
M C M X X X I X
MCMXXXIX uses the subtractive pair IX: one before ten — ten minus one.
Binary
1 1 1 1 0 0 1 0 0 1 1
1 × 1,024 + 1 × 512 + 1 × 256 + 1 × 128 + 0 × 64 + 0 × 32 + 1 × 16 + 0 × 8 + 0 × 4 + 1 × 2 + 1 × 1 = 1,939
Octal
3 6 2 3
3 × 512 + 6 × 64 + 2 × 8 + 3 × 1 = 1,939
Hexadecimal
7 9 3
7 × 256 + 9 × 16 + 3 × 1 = 1,939
Read as powers of two: 1,024 + 512 + 256 + 128 + 16 + 2 + 1 = 1,939.
In historical numeral systems
Egyptian
1 lotus, 9 coils of rope, 3 hobbles, 9 strokes
1 × 1,000 + 9 × 100 + 3 × 10 + 9 × 1 = 1,939. 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), 1 corner wedge + 9 vertical wedges (units place)
32 × 60 + 19 = 1939. 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
Related numbers & connections
1939 is a year in the 20th century, in the 1930s.
The Normandy landings came five years into a war that had begun in Europe in 1939, and nearly three years after the Eastern Front opened.
View 1944 →Numbers Around Us
- appears inHistorical years
why?
Strength 0.50, confidence "high".
- appears alongside1945
why?
Strength 0.50, confidence "high".
History
In 1939, the Second World War began with the invasion of Poland.
DocumentedHistoryGeography: globalPeriod: 1939Germany invaded Poland on 1 September 1939 and Britain and France declared war two days later. Dating the Second World War from 1939 reflects a European vantage point: full-scale war in Asia had been under way since Japan's invasion of China in 1937.
DocumentedHistoryGeography: EuropePeriod: 1939
Science
In 1939, Lise Meitner and Otto Frisch explained the splitting of the uranium nucleus and named it fission, calculating the energy it would release (Sweden and Denmark).
DocumentedScienceGeography: Sweden and DenmarkPeriod: 1939
Common questions
Is 1939 a prime number?
No, 1939 is not prime.
What are the factors of 1939?
The factors of 1939 are 1, 7, 277, 1939.
What is 1939 in Roman numerals?
1939 in Roman numerals is MCMXXXIX. IX is subtractive: one before ten — ten minus one. Written additively it would be MDCCCCXXXVIIII, 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