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.
1639 is part of
Factors & digit properties
- Divisors (4)
- 1, 11, 149, 1639
- Prime factorisation
- 11 × 149
- Digit sum
- 19
- Digital root
- 1
Representations
- Decimal
- 1639
- Scientific notation
- 1.639 × 10^3
Roman numerals
M D C X X X I X
MDCXXXIX uses the subtractive pair IX: one before ten — ten minus one.
Binary
1 1 0 0 1 1 0 0 1 1 1
1 × 1,024 + 1 × 512 + 0 × 256 + 0 × 128 + 1 × 64 + 1 × 32 + 0 × 16 + 0 × 8 + 1 × 4 + 1 × 2 + 1 × 1 = 1,639
Octal
3 1 4 7
3 × 512 + 1 × 64 + 4 × 8 + 7 × 1 = 1,639
Hexadecimal
6 6 7
6 × 256 + 6 × 16 + 7 × 1 = 1,639
Read as powers of two: 1,024 + 512 + 64 + 32 + 4 + 2 + 1 = 1,639.
In historical numeral systems
Egyptian
1 lotus, 6 coils of rope, 3 hobbles, 9 strokes
1 × 1,000 + 6 × 100 + 3 × 10 + 9 × 1 = 1,639. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
2 corner wedges + 7 vertical wedges (sixties place), 1 corner wedge + 9 vertical wedges (units place)
27 × 60 + 19 = 1639. 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
- Lucky number (mathematical sieve)
Related numbers & connections
1639 is a year in the 17th century, in the 1630s.
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 →Numbers Around Us
- appears inHistorical years
why?
Strength 0.50, confidence "high".
Other connections
- developed from1609
why?
Strength 0.50, confidence "high".
Science
In 1639, Jeremiah Horrocks made the first recorded observation of a transit of Venus, having predicted it when established tables did not (England).
DocumentedScienceGeography: EnglandPeriod: 1639The 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. IX is subtractive: one before ten — ten minus one. Written additively it would be MDCXXXVIIII, 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