445
Port 445 carries SMB, the Windows file-sharing protocol.
- Odd
- Composite
Where 445 fits
Why 445 is special
445 is the port that carried WannaCry and NotPetya across networks in 2017. Both exploited a flaw in SMB to spread without anyone opening anything, which is why blocking 445 at the network edge became standard advice and remains so.
Factors & digit properties
- Divisors (4)
- 1, 5, 89, 445
- Prime factorisation
- 5 × 89
- Digit sum
- 13
- Digital root
- 4
Representations
- Decimal
- 445
- Scientific notation
- 4.450 × 10^2
Roman numerals
C D X L V
CDXLV uses the subtractive pair XL: ten before fifty — fifty minus ten.
Binary
1 1 0 1 1 1 1 0 1
1 × 256 + 1 × 128 + 0 × 64 + 1 × 32 + 1 × 16 + 1 × 8 + 1 × 4 + 0 × 2 + 1 × 1 = 445
Octal
6 7 5
6 × 64 + 7 × 8 + 5 × 1 = 445
Hexadecimal
1 b d
1 × 256 + b × 16 + d × 1 = 445
Read as powers of two: 256 + 128 + 32 + 16 + 8 + 4 + 1 = 445.
In historical numeral systems
Egyptian
4 coils of rope, 4 hobbles, 5 strokes
4 × 100 + 4 × 10 + 5 × 1 = 445. 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 + 5 vertical wedges (units place)
7 × 60 + 25 = 445. Places are separated by a space on the tablet, with the higher place written first.
Greek (Ionic)
upsilon, then mu, then epsilon, marked as a numeral
upsilon-mu-epsilon + keraia
upsilon + mu + 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 mem, then he
tav-mem-he
tav (400) + mem (40) + he (5) = 445, 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
Related numbers & connections
The Windows RPC endpoint mapper and SMB are blocked together at essentially every network perimeter, and 445 is the port the 2017 ransomware worms travelled on.
View 135 →Technology & computing
WannaCry and NotPetya both spread through SMB on port 445 in 2017, using a flaw that required no user action at all. That is why blocking 445 at the network perimeter went from good practice to standard advice, and why it has stayed there.
DocumentedTechnology & computing
Common questions
Is 445 a prime number?
No, 445 is not prime.
What are the factors of 445?
The factors of 445 are 1, 5, 89, 445.
What is 445 in Roman numerals?
445 in Roman numerals is CDXLV. XL is subtractive: ten before fifty — fifty minus ten. Written additively it would be CCCCXXXXV, 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