643
643 is the ISO 3166-1 numeric country code for Russia.
- Odd
- Prime
Where 643 fits
Why 643 is special
Russia inherited the Soviet Union's seat in most international systems but not its country code — the USSR's code was retired and Russia assigned a new one.
643 is part of
Factors & digit properties
- Divisors (2)
- 1, 643
- Prime factorisation
- 643
- Digit sum
- 13
- Digital root
- 4
Representations
- Decimal
- 643
- Scientific notation
- 6.430 × 10^2
Roman numerals
D C X L I I I
DCXLIII uses the subtractive pair XL: ten before fifty — fifty minus ten.
Binary
1 0 1 0 0 0 0 0 1 1
1 × 512 + 0 × 256 + 1 × 128 + 0 × 64 + 0 × 32 + 0 × 16 + 0 × 8 + 0 × 4 + 1 × 2 + 1 × 1 = 643
Octal
1 2 0 3
1 × 512 + 2 × 64 + 0 × 8 + 3 × 1 = 643
Hexadecimal
2 8 3
2 × 256 + 8 × 16 + 3 × 1 = 643
Read as powers of two: 512 + 128 + 2 + 1 = 643.
In historical numeral systems
Egyptian
6 coils of rope, 4 hobbles, 3 strokes
6 × 100 + 4 × 10 + 3 × 1 = 643. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
1 corner wedge (sixties place), 4 corner wedges + 3 vertical wedges (units place)
10 × 60 + 43 = 643. Places are separated by a space on the tablet, with the higher place written first.
Greek (Ionic)
chi, then mu, then gamma, marked as a numeral
chi-mu-gamma + keraia
chi + mu + gamma 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 resh, then mem, then gimel
tav-resh-mem-gimel
tav (400) + resh (200) + mem (40) + gimel (3) = 643, 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
- Lucky number (mathematical sieve)
- Twin prime
Related numbers & connections
Russia's ISO numeric code and calling code. Russia kept the Soviet calling code +7 and was assigned a new ISO code, so the two systems took opposite decisions about succession.
View 7 →Other connections
- is associated with7
why?
Strength 0.50, confidence "high".
Geography
643 is Russia's ISO numeric code. The Soviet code was retired rather than transferred, which is a small technical statement about succession that took diplomats considerably longer to settle.
DocumentedGeographyGeography: Russia
Common questions
Is 643 a prime number?
Yes, 643 is prime — it has exactly two positive divisors: 1 and itself.
What are the factors of 643?
The factors of 643 are 1, 643.
What is 643 in Roman numerals?
643 in Roman numerals is DCXLIII. XL is subtractive: ten before fifty — fifty minus ten. Written additively it would be DCXXXXIII, 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