1639
1639 is the year the first transit of Venus was observed.
- Odd
- Composite
Where 1639 fits
Why 1639 is special
Two young English astronomers observed it after one of them corrected the published tables. Transits come in pairs eight years apart and then not for over a century.
Factors & digit properties
- Divisors (4)
- 1, 11, 149, 1639
- Prime factorisation
- 11 × 149
- Digit sum
- 19
- Digital root
- 1
Representations
- Decimal
- 1639
- Binary
- 11001100111
- Octal
- 3147
- Hexadecimal
- 667
- Roman numeral
- MDCXXXIX
- Scientific notation
- 1.639 × 10^3
Other mathematical patterns
- Deficient number
- Semiprime
- Lucky number (mathematical sieve)
Related numbers & connections
Kepler published his first two laws in 1609, and correcting his tables is what let Horrocks predict and observe the 1639 transit of Venus.
View 1609 →Other connections
- developed from1609
why?
Strength 0.50, confidence "high".
Science
The 1639 Venus transit was seen by Jeremiah Horrocks and William Crabtree, apparently the only observers anywhere, after Horrocks corrected Kepler's tables. The next pair did not come until 1761.
DocumentedScienceGeography: EnglandPeriod: 1639
Common questions
Is 1639 a prime number?
No, 1639 is not prime.
What are the factors of 1639?
The factors of 1639 are 1, 11, 149, 1639.
What is 1639 in Roman numerals?
1639 in Roman numerals is MDCXXXIX.
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