869
NGC 869 is one half of the Double Cluster in Perseus.
- Odd
- Composite
Where 869 fits
Why 869 is special
It and NGC 884 are genuinely near each other in space rather than merely aligned, which is unusual for a pair that looks like a coincidence.
Factors & digit properties
- Divisors (4)
- 1, 11, 79, 869
- Prime factorisation
- 11 × 79
- Digit sum
- 23
- Digital root
- 5
Representations
- Decimal
- 869
- Scientific notation
- 8.690 × 10^2
Roman numerals
D C C C L X I X
DCCCLXIX uses the subtractive pair IX: one before ten — ten minus one.
Binary
1 1 0 1 1 0 0 1 0 1
1 × 512 + 1 × 256 + 0 × 128 + 1 × 64 + 1 × 32 + 0 × 16 + 0 × 8 + 1 × 4 + 0 × 2 + 1 × 1 = 869
Octal
1 5 4 5
1 × 512 + 5 × 64 + 4 × 8 + 5 × 1 = 869
Hexadecimal
3 6 5
3 × 256 + 6 × 16 + 5 × 1 = 869
Read as powers of two: 512 + 256 + 64 + 32 + 4 + 1 = 869.
In historical numeral systems
Egyptian
8 coils of rope, 6 hobbles, 9 strokes
8 × 100 + 6 × 10 + 9 × 1 = 869. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
1 corner wedge + 4 vertical wedges (sixties place), 2 corner wedges + 9 vertical wedges (units place)
14 × 60 + 29 = 869. Places are separated by a space on the tablet, with the higher place written first.
Greek (Ionic)
omega, then xi, then theta, marked as a numeral
omega-xi-theta + keraia
omega + xi + theta written in descending order and added — the letters carry their values wherever they stand, so this is addition, not place value.
Hebrew numerals
tav, then tav, then samekh, then tet
tav-tav-samekh-tet
tav (400) + tav (400) + samekh (60) + tet (9) = 869, written in descending order.
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
The Double Cluster is a genuine physical pair at the same distance rather than a line-of-sight coincidence.
View 884 →Numbers Around Us
- appears alongside884
why?
Strength 0.50, confidence "high".
Science
NGC 869 and NGC 884 are open clusters of similar age and distance in the Perseus arm, forming a physically associated pair rather than a chance superposition.
DocumentedSciencePeriod: antiquity–
Common questions
Is 869 a prime number?
No, 869 is not prime.
What are the factors of 869?
The factors of 869 are 1, 11, 79, 869.
What is 869 in Roman numerals?
869 in Roman numerals is DCCCLXIX. IX is subtractive: one before ten — ten minus one. Written additively it would be DCCCLXVIIII, 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: 1 reviewer-confirmed record, sourced and reviewed before publication.
Last reviewed: 15 July 2026