139
Port 139 carries Windows file sharing over the older NetBIOS session service.
- Odd
- Prime
Where 139 fits
Why 139 is special
139 is the predecessor of 445, and both are blocked together at network perimeters. It survives because some equipment never moved on, which is the usual reason an obsolete port is still worth knowing about.
139 is part of
Factors & digit properties
- Divisors (2)
- 1, 139
- Prime factorisation
- 139
- Digit sum
- 13
- Digital root
- 4
Representations
- Decimal
- 139
- Binary
- 10001011
- Octal
- 213
- Hexadecimal
- 8b
- Roman numeral
- CXXXIX
- Scientific notation
- 1.390 × 10^2
Other mathematical patterns
- Deficient number
- Happy number
- Twin prime
Related numbers & connections
Both carry Windows file sharing — 139 over the older NetBIOS layer and 445 directly over TCP. Blocking both at the network edge is standard practice after the 2017 worms.
View 445 →Other connections
- is associated with445
why?
Strength 0.50, confidence "high".
Technology & computing
139 carries Windows file sharing over NetBIOS and 445 carries it directly over TCP. Both are blocked together at network perimeters, and 139 persists mainly on equipment that was never updated — which is the usual reason an obsolete port still matters.
DocumentedTechnology & computing
Common questions
Is 139 a prime number?
Yes, 139 is prime — it has exactly two positive divisors: 1 and itself.
What are the factors of 139?
The factors of 139 are 1, 139.
What is 139 in Roman numerals?
139 in Roman numerals is CXXXIX.
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