1591
1591 is the year Galileo is said to have dropped weights from the Leaning Tower of Pisa.
- Odd
- Composite
Where 1591 fits
Why 1591 is special
The story comes from a biography written decades later by his assistant and is not corroborated. Galileo did establish the result, by rolling balls down inclined planes where timing was possible.
1591 connects to:
- historical years — appears in
- 1610 — contrasts with
Same number, different meanings
How 1591 is understood across different contexts — never implying one meaning because of another.
- Mathematics
The story comes from a biography written decades later by his assistant and is not corroborated. Galileo did establish the result, by rolling balls down inclined planes where timing was possible.
- History
In 1591, François Viète introduced systematic algebraic notation using letters for both knowns and unknowns (France).
- Science
The Pisa demonstration is attested only by Viviani, writing long afterwards. Galileo reached the same conclusion using inclined planes, which he could actually time — the real method is less memorable and better evidence.
1591 is part of
Factors & digit properties
- Divisors (4)
- 1, 37, 43, 1591
- Prime factorisation
- 37 × 43
- Digit sum
- 16
- Digital root
- 7
Representations
- Decimal
- 1591
- Scientific notation
- 1.591 × 10^3
Roman numerals
M D X C I
MDXCI uses the subtractive pair XC: ten before a hundred — a hundred minus ten.
Binary
1 1 0 0 0 1 1 0 1 1 1
1 × 1,024 + 1 × 512 + 0 × 256 + 0 × 128 + 0 × 64 + 1 × 32 + 1 × 16 + 0 × 8 + 1 × 4 + 1 × 2 + 1 × 1 = 1,591
Octal
3 0 6 7
3 × 512 + 0 × 64 + 6 × 8 + 7 × 1 = 1,591
Hexadecimal
6 3 7
6 × 256 + 3 × 16 + 7 × 1 = 1,591
Read as powers of two: 1,024 + 512 + 32 + 16 + 4 + 2 + 1 = 1,591.
In historical numeral systems
Egyptian
1 lotus, 5 coils of rope, 9 hobbles, 1 stroke
1 × 1,000 + 5 × 100 + 9 × 10 + 1 × 1 = 1,591. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
2 corner wedges + 6 vertical wedges (sixties place), 3 corner wedges + 1 vertical wedge (units place)
26 × 60 + 31 = 1591. 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
1591 is a year in the 16th century, in the 1590s.
The Pisa tower experiment attributed to Galileo around 1591 is almost certainly apocryphal, while his 1610 telescopic observations are documented in his own published work.
View 1610 →Numbers Around Us
- appears inHistorical years
why?
Strength 0.50, confidence "high".
Other connections
- contrasts with1610
why?
Strength 0.50, confidence "high".
History
In 1591, François Viète introduced systematic algebraic notation using letters for both knowns and unknowns (France).
DocumentedHistoryGeography: FrancePeriod: 1591
Science
The Pisa demonstration is attested only by Viviani, writing long afterwards. Galileo reached the same conclusion using inclined planes, which he could actually time — the real method is less memorable and better evidence.
DocumentedScienceGeography: ItalyPeriod: 1591
Common questions
Is 1591 a prime number?
No, 1591 is not prime.
What are the factors of 1591?
The factors of 1591 are 1, 37, 43, 1591.
What is 1591 in Roman numerals?
1591 in Roman numerals is MDXCI. XC is subtractive: ten before a hundred — a hundred minus ten. Written additively it would be MDLXXXXI, 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