443
443 is the standard port for HTTPS — encrypted web traffic.
- Odd
- Prime
Where 443 fits
Why 443 is special
443 is the number that made the padlock possible. Plain HTTP took port 80 and encrypted HTTP was assigned 443 alongside it, so a browser can tell from the address alone which it is speaking. As the web moved to encryption by default, 443 went from the exception to carrying nearly all of it.
Same number, different meanings
How 443 is understood across different contexts — never implying one meaning because of another.
- Mathematics
443 is the number that made the padlock possible. Plain HTTP took port 80 and encrypted HTTP was assigned 443 alongside it, so a browser can tell from the address alone which it is speaking. As the web moved to encryption by default, 443 went from the exception to carrying nearly all of it.
- Everyday life
The padlock indicates that the connection to the site is encrypted and that the certificate matches the domain. It makes no claim about who runs the site or whether it is trustworthy, which is why phishing sites routinely display one.
- History
HTTPS was introduced by Netscape in 1994 and remained a minority of web traffic for two decades, largely because certificates cost money and required manual renewal. Automated free issuance from 2016 moved encrypted traffic past half of page loads within about two years.
- Technology & computing
The default TCP port for HTTPS is 443 (worldwide, IANA registry).
- Science
IC 443, the Jellyfish Nebula, is a supernova remnant whose expansion into an adjacent molecular cloud produces distinctive shocked emission.
Factors & digit properties
- Divisors (2)
- 1, 443
- Prime factorisation
- 443
- Digit sum
- 11
- Digital root
- 2
Representations
- Decimal
- 443
- Scientific notation
- 4.430 × 10^2
Roman numerals
C D X L I I I
CDXLIII uses the subtractive pair XL: ten before fifty — fifty minus ten.
Binary
1 1 0 1 1 1 0 1 1
1 × 256 + 1 × 128 + 0 × 64 + 1 × 32 + 1 × 16 + 1 × 8 + 0 × 4 + 1 × 2 + 1 × 1 = 443
Octal
6 7 3
6 × 64 + 7 × 8 + 3 × 1 = 443
Hexadecimal
1 b b
1 × 256 + b × 16 + b × 1 = 443
Read as powers of two: 256 + 128 + 32 + 16 + 8 + 2 + 1 = 443.
In historical numeral systems
Egyptian
4 coils of rope, 4 hobbles, 3 strokes
4 × 100 + 4 × 10 + 3 × 1 = 443. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
7 vertical wedges (sixties place), 2 corner wedges + 3 vertical wedges (units place)
7 × 60 + 23 = 443. Places are separated by a space on the tablet, with the higher place written first.
Greek (Ionic)
upsilon, then mu, then gamma, marked as a numeral
upsilon-mu-gamma + keraia
upsilon + 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 mem, then gimel
tav-mem-gimel
tav (400) + mem (40) + gimel (3) = 443, 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
- Sophie Germain prime
Related numbers & connections
Port 443 is an IANA assignment. The number itself carries no meaning; its authority comes entirely from the registry entry.
OpenVPN's own port is easy to identify and therefore easy to block, so it is frequently moved to 443 where it cannot readily be told apart from ordinary web traffic.
View 1194 →Numbers Around Us
- appears inNumbers assigned as identifiers
why?
Strength 0.50, confidence "high".
- appears inNumbers that make the internet work
why?
Strength 0.50, confidence "high".
Other connections
- contrasts with1194
why?
Strength 0.50, confidence "high".
- contrasts with9418
why?
Strength 0.50, confidence "high".
- contrasts with80
why?
Strength 0.50, confidence "high".
- is associated with993
why?
Strength 0.50, confidence "high".
- is associated with3546
why?
Strength 0.50, confidence "high".
- is associated with2818
why?
Strength 0.50, confidence "high".
- is associated with127
why?
Strength 0.50, confidence "high".
Everyday life
The padlock indicates that the connection to the site is encrypted and that the certificate matches the domain. It makes no claim about who runs the site or whether it is trustworthy, which is why phishing sites routinely display one.
DocumentedEveryday lifeGeography: GlobalPeriod: 1994–
History
HTTPS was introduced by Netscape in 1994 and remained a minority of web traffic for two decades, largely because certificates cost money and required manual renewal. Automated free issuance from 2016 moved encrypted traffic past half of page loads within about two years.
DocumentedHistoryGeography: International — IANA and IETFPeriod: 1994–
Technology & computing
The default TCP port for HTTPS is 443 (worldwide, IANA registry).
DocumentedTechnology & computingGeography: worldwide, IANA registryAssigning encrypted HTTP its own port meant a browser could tell from the URL alone which protocol to speak, before any connection was made. As the web moved to encryption by default, traffic shifted almost entirely from 80 to 443 — one of the largest changes in what the internet carries, visible only as a number.
DocumentedTechnology & computing
Science
IC 443, the Jellyfish Nebula, is a supernova remnant whose expansion into an adjacent molecular cloud produces distinctive shocked emission.
DocumentedSciencePeriod: 1890s–
Common questions
Is 443 a prime number?
Yes, 443 is prime — it has exactly two positive divisors: 1 and itself.
What are the factors of 443?
The factors of 443 are 1, 443.
What is 443 in Roman numerals?
443 in Roman numerals is CDXLIII. XL is subtractive: ten before fifty — fifty minus ten. Written additively it would be CCCCXXXXIII, 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: 5 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 15 July 2026