993
Port 993 carries IMAP over TLS — encrypted mail reading.
- Odd
- Composite
Where 993 fits
Why 993 is special
993 pairs with 143 the way 443 pairs with 80: same protocol, encrypted from the first byte rather than upgraded mid-conversation. Mail clients default to it now, which is why a mail password is no longer readable by anyone sharing the network.
Factors & digit properties
- Divisors (4)
- 1, 3, 331, 993
- Prime factorisation
- 3 × 331
- Digit sum
- 21
- Digital root
- 3
Representations
- Decimal
- 993
- Scientific notation
- 9.930 × 10^2
Roman numerals
C M X C I I I
CMXCIII uses the subtractive pair XC: ten before a hundred — a hundred minus ten.
Binary
1 1 1 1 1 0 0 0 0 1
1 × 512 + 1 × 256 + 1 × 128 + 1 × 64 + 1 × 32 + 0 × 16 + 0 × 8 + 0 × 4 + 0 × 2 + 1 × 1 = 993
Octal
1 7 4 1
1 × 512 + 7 × 64 + 4 × 8 + 1 × 1 = 993
Hexadecimal
3 e 1
3 × 256 + e × 16 + 1 × 1 = 993
Read as powers of two: 512 + 256 + 128 + 64 + 32 + 1 = 993.
In historical numeral systems
Egyptian
9 coils of rope, 9 hobbles, 3 strokes
9 × 100 + 9 × 10 + 3 × 1 = 993. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
1 corner wedge + 6 vertical wedges (sixties place), 3 corner wedges + 3 vertical wedges (units place)
16 × 60 + 33 = 993. Places are separated by a space on the tablet, with the higher place written first.
Greek (Ionic)
sampi, then koppa, then gamma, marked as a numeral
sampi-koppa-gamma + keraia
sampi + koppa + 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 tav, then qof, then tsadi, then gimel
tav-tav-qof-tsadi-gimel
tav (400) + tav (400) + qof (100) + tsadi (90) + gimel (3) = 993, 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
- Lucky number (mathematical sieve)
Related numbers & connections
Both are the TLS-from-the-first-byte version of an older plaintext port. The pattern — a separate port rather than an in-band upgrade — repeats across the protocols that moved to encryption early.
View 443 →Other connections
- is associated with443
why?
Strength 0.50, confidence "high".
Technology & computing
993 is to 143 what 443 is to 80 — the same protocol wrapped in TLS from the start rather than upgraded mid-conversation. Clients default to it now, which is why a mail password is no longer readable by anyone sharing a network.
DocumentedTechnology & computing
Common questions
Is 993 a prime number?
No, 993 is not prime.
What are the factors of 993?
The factors of 993 are 1, 3, 331, 993.
What is 993 in Roman numerals?
993 in Roman numerals is CMXCIII. XC is subtractive: ten before a hundred — a hundred minus ten. Written additively it would be DCCCCLXXXXIII, 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