12,345
Port 12345 was the NetBus trojan's default.
- Odd
- Composite
Where 12,345 fits
Why 12,345 is special
Chosen for being trivially memorable, it became one of the most scanned ports of the late 1990s. Its obviousness is why it appears in security teaching to this day.
Factors & digit properties
- Divisors (8)
- 1, 3, 5, 15, 823, 2469, 4115, 12345
- Prime factorisation
- 3 × 5 × 823
- Digit sum
- 15
- Digital root
- 6
Representations
- Decimal
- 12345
- Scientific notation
- 1.235 × 10^4
Roman numerals
Roman numerals as modelled here goes up to 3,999.
Binary
1 1 0 0 0 0 0 0 1 1 1 0 0 1
1 × 8,192 + 1 × 4,096 + 0 × 2,048 + 0 × 1,024 + 0 × 512 + 0 × 256 + 0 × 128 + 0 × 64 + 1 × 32 + 1 × 16 + 1 × 8 + 0 × 4 + 0 × 2 + 1 × 1 = 12,345
Octal
3 0 0 7 1
3 × 4,096 + 0 × 512 + 0 × 64 + 7 × 8 + 1 × 1 = 12,345
Hexadecimal
3 0 3 9
3 × 4,096 + 0 × 256 + 3 × 16 + 9 × 1 = 12,345
Read as powers of two: 8,192 + 4,096 + 32 + 16 + 8 + 1 = 12,345.
In historical numeral systems
Egyptian
1 finger, 2 lotuses, 3 coils of rope, 4 hobbles, 5 strokes
1 × 10,000 + 2 × 1,000 + 3 × 100 + 4 × 10 + 5 × 1 = 12,345. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
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
- Harshad (Niven) number
Related numbers & connections
Metasploit's default listener and the NetBus trojan's default port are both indicators of compromise precisely because they are defaults. Competent attackers change them.
View 4444 →Other connections
- is associated with4444
why?
Strength 0.50, confidence "high".
Technology & computing
NetBus used 12345 because it is the easiest number to remember, which made detection equally easy. It remains a teaching example of why obscurity chosen for convenience is not security.
DocumentedTechnology & computingPeriod: 1998
Common questions
Is 12,345 a prime number?
No, 12,345 is not prime.
What are the factors of 12,345?
The factors of 12,345 are 1, 3, 5, 15, 823, 2469, 4115, 12345.
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