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.
Factors & digit properties
- Divisors (4)
- 1, 37, 43, 1591
- Prime factorisation
- 37 × 43
- Digit sum
- 16
- Digital root
- 7
Representations
- Decimal
- 1591
- Binary
- 11000110111
- Octal
- 3067
- Hexadecimal
- 637
- Roman numeral
- MDXCI
- Scientific notation
- 1.591 × 10^3
Other mathematical patterns
- Deficient number
- Semiprime
Related numbers & connections
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 →Other connections
- contrasts with1610
why?
Strength 0.50, confidence "high".
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.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 1 reviewer-confirmed record, sourced and reviewed before publication.
Last reviewed: 3 August 2026