321
The Airbus A321 is the stretched A320 and now outsells the aircraft it was stretched from.
- Odd
- Composite
Where 321 fits
Why 321 is special
Its long-range variant can cross the Atlantic, which lets airlines fly thin routes that could not fill a widebody — the gap the Boeing 757 used to occupy.
Factors & digit properties
- Divisors (4)
- 1, 3, 107, 321
- Prime factorisation
- 3 × 107
- Digit sum
- 6
- Digital root
- 6
Representations
- Decimal
- 321
- Scientific notation
- 3.210 × 10^2
Roman numerals
C C C X X I
Binary
1 0 1 0 0 0 0 0 1
1 × 256 + 0 × 128 + 1 × 64 + 0 × 32 + 0 × 16 + 0 × 8 + 0 × 4 + 0 × 2 + 1 × 1 = 321
Octal
5 0 1
5 × 64 + 0 × 8 + 1 × 1 = 321
Hexadecimal
1 4 1
1 × 256 + 4 × 16 + 1 × 1 = 321
Read as powers of two: 256 + 64 + 1 = 321.
In historical numeral systems
Egyptian
3 coils of rope, 2 hobbles, 1 stroke
3 × 100 + 2 × 10 + 1 × 1 = 321. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
5 vertical wedges (sixties place), 2 corner wedges + 1 vertical wedge (units place)
5 × 60 + 21 = 321. Places are separated by a space on the tablet, with the higher place written first.
Greek (Ionic)
tau, then kappa, then alpha, marked as a numeral
tau-kappa-alpha + keraia
tau + kappa + alpha written in descending order and added — the letters carry their values wherever they stand, so this is addition, not place value.
Hebrew numerals
shin, then kaf, then alef
shin-kaf-alef
shin (300) + kaf (20) + alef (1) = 321, written in descending order.
Maya
3 bars + 1 dot (upper, twenties place) over 1 dot (lower, units place)
16 × 20 + 1 = 321. Places stack vertically with the smallest at the bottom, so the upper group is worth twenty times the lower.
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
The A321 is the stretched A320 and now outsells it, because its long-range variants fly thin transatlantic routes that cannot fill a widebody.
View 320 →Other connections
- contrasts with320
why?
Strength 0.50, confidence "high".
Technology & computing
The A321LR and XLR fly transatlantic routes too thin for a widebody, which is the role the 757 held until production ended in 2004. The gap stayed open for roughly fifteen years.
DocumentedTechnology & computing
Common questions
Is 321 a prime number?
No, 321 is not prime.
What are the factors of 321?
The factors of 321 are 1, 3, 107, 321.
What is 321 in Roman numerals?
321 in Roman numerals is CCCXXI.
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