465
Port 465 carries SMTP over TLS for submitting mail.
- Odd
- Composite
Where 465 fits
Why 465 is special
465 was assigned for encrypted mail submission, deprecated in favour of STARTTLS on 587, and then reinstated in 2018 when implicit TLS proved the more reliable design. It is one of the clearer cases of a standards body reversing itself on evidence.
465 is part of
Factors & digit properties
- Divisors (8)
- 1, 3, 5, 15, 31, 93, 155, 465
- Prime factorisation
- 3 × 5 × 31
- Digit sum
- 15
- Digital root
- 6
Representations
- Decimal
- 465
- Scientific notation
- 4.650 × 10^2
Roman numerals
C D L X V
CDLXV uses the subtractive pair CD: a hundred before five hundred — five hundred minus a hundred.
Binary
1 1 1 0 1 0 0 0 1
1 × 256 + 1 × 128 + 1 × 64 + 0 × 32 + 1 × 16 + 0 × 8 + 0 × 4 + 0 × 2 + 1 × 1 = 465
Octal
7 2 1
7 × 64 + 2 × 8 + 1 × 1 = 465
Hexadecimal
1 d 1
1 × 256 + d × 16 + 1 × 1 = 465
Read as powers of two: 256 + 128 + 64 + 16 + 1 = 465.
In historical numeral systems
Egyptian
4 coils of rope, 6 hobbles, 5 strokes
4 × 100 + 6 × 10 + 5 × 1 = 465. 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), 4 corner wedges + 5 vertical wedges (units place)
7 × 60 + 45 = 465. Places are separated by a space on the tablet, with the higher place written first.
Greek (Ionic)
upsilon, then xi, then epsilon, marked as a numeral
upsilon-xi-epsilon + keraia
upsilon + xi + epsilon 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 samekh, then he
tav-samekh-he
tav (400) + samekh (60) + he (5) = 465, 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
- Triangular number
- Deficient number
- Harshad (Niven) number
Related numbers & connections
Two routes to encrypted mail submission: implicit TLS on 465 and an upgrade from plaintext on 587. 465 was deprecated in favour of 587 and then reinstated in 2018, which is a rare reversal for a standards body.
View 587 →Other connections
- contrasts with587
why?
Strength 0.50, confidence "high".
Technology & computing
465 was assigned for implicit TLS mail submission, deprecated in favour of upgrading a plain connection on 587, then formally reinstated in 2018 when implicit TLS proved more reliable in practice. Standards rarely reverse this cleanly, which is what makes it worth recording.
DocumentedTechnology & computing
Common questions
Is 465 a prime number?
No, 465 is not prime.
What are the factors of 465?
The factors of 465 are 1, 3, 5, 15, 31, 93, 155, 465.
What is 465 in Roman numerals?
465 in Roman numerals is CDLXV. CD is subtractive: a hundred before five hundred — five hundred minus a hundred. Written additively it would be CCCCLXV, 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