1900
1900 was not a leap year, and port 1900 carries UPnP device discovery.
- Even
- Composite
Where 1900 fits
Why 1900 is special
The two are unrelated. Years divisible by 100 skip the leap day unless also divisible by 400, so 1900 had no 29 February while 2000 did. A great deal of software has been written that gets this wrong, because the exception only bites twice in four centuries.
Same number, different meanings
How 1900 is understood across different contexts — never implying one meaning because of another.
- Mathematics
The two are unrelated. Years divisible by 100 skip the leap day unless also divisible by 400, so 1900 had no 29 February while 2000 did. A great deal of software has been written that gets this wrong, because the exception only bites twice in four centuries.
- History
In 1900, Max Planck introduced the quantum hypothesis, and Freud published The Interpretation of Dreams (Europe).
- Science
A year divisible by 100 is not a leap year unless it is also divisible by 400. So 1900 had no 29 February and 2000 did — and any software tested only around 2000 got the right answer for the wrong reason. The next test is 2100.
1900 is part of
Factors & digit properties
- Divisors (18)
- 1, 2, 4, 5, 10, 19, 20, 25, 38, 50, 76, 95, 100, 190, 380, 475, 950, 1900
- Prime factorisation
- 2^2 × 5^2 × 19
- Digit sum
- 10
- Digital root
- 1
Representations
- Decimal
- 1900
- Scientific notation
- 1.900 × 10^3
Roman numerals
M C M
MCM uses the subtractive pair CM: a hundred before a thousand — a thousand minus a hundred.
Binary
1 1 1 0 1 1 0 1 1 0 0
1 × 1,024 + 1 × 512 + 1 × 256 + 0 × 128 + 1 × 64 + 1 × 32 + 0 × 16 + 1 × 8 + 1 × 4 + 0 × 2 + 0 × 1 = 1,900
Octal
3 5 5 4
3 × 512 + 5 × 64 + 5 × 8 + 4 × 1 = 1,900
Hexadecimal
7 6 c
7 × 256 + 6 × 16 + c × 1 = 1,900
Read as powers of two: 1,024 + 512 + 256 + 64 + 32 + 8 + 4 = 1,900.
In historical numeral systems
Egyptian
1 lotus, 9 coils of rope
1 × 1,000 + 9 × 100 = 1,900. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
3 corner wedges + 1 vertical wedge (sixties place), 4 corner wedges (units place)
31 × 60 + 40 = 1900. 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
- Happy number
- Harshad (Niven) number
Related numbers & connections
1900 is a year in the 19th century, in the 1900s.
1900 was not a leap year and 2000 was. The rule skips the leap day in century years unless they divide by 400, which means the exception has been tested exactly once since the calendar was adopted.
View 2000 →History
In 1900, Max Planck introduced the quantum hypothesis, and Freud published The Interpretation of Dreams (Europe).
DocumentedHistoryGeography: EuropePeriod: 1900
Science
A year divisible by 100 is not a leap year unless it is also divisible by 400. So 1900 had no 29 February and 2000 did — and any software tested only around 2000 got the right answer for the wrong reason. The next test is 2100.
DocumentedScience
Common questions
Is 1900 a prime number?
No, 1900 is not prime.
What are the factors of 1900?
The factors of 1900 are 1, 2, 4, 5, 10, 19, 20, 25, 38, 50, 76, 95, 100, 190, 380, 475, 950, 1900.
What is 1900 in Roman numerals?
1900 in Roman numerals is MCM. CM is subtractive: a hundred before a thousand — a thousand minus a hundred. Written additively it would be MDCCCC, 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