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
- Binary
- 110111101
- Octal
- 675
- Hexadecimal
- 1bd
- Roman numeral
- CDXLV
- Scientific notation
- 4.450 × 10^2
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.
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: 3 August 2026