1521
Port 1521 is the default port for Oracle Database.
Where 1521 fits
Why 1521 is special
1521 completes the set of default database ports alongside MySQL's 3306, PostgreSQL's 5432 and SQL Server's 1433. Oracle's listener historically returned useful information before authentication, which made an exposed 1521 a reconnaissance tool as much as a login prompt.
1521 connects to:
- historical years — appears in
- 1433 — appears alongside
Same number, different meanings
How 1521 is understood across different contexts — never implying one meaning because of another.
- Mathematics
1521 completes the set of default database ports alongside MySQL's 3306, PostgreSQL's 5432 and SQL Server's 1433. Oracle's listener historically returned useful information before authentication, which made an exposed 1521 a reconnaissance tool as much as a login prompt.
- History
In 1521, Tenochtitlan fell to Cortes and his allied city-states after a siege (Mesoamerica).
- Technology & computing
With 3306, 5432 and 1433, Oracle's 1521 completes the set of database ports scanning tools check by default. Oracle's listener historically disclosed version and service information before authentication, making an exposed port useful to an attacker before any login was attempted.
1521 is part of
Factors & digit properties
- Divisors (9)
- 1, 3, 9, 13, 39, 117, 169, 507, 1521
- Prime factorisation
- 3^2 × 13^2
- Digit sum
- 9
- Digital root
- 9
Representations
- Decimal
- 1521
- Scientific notation
- 1.521 × 10^3
Roman numerals
M D X X I
Binary
1 0 1 1 1 1 1 0 0 0 1
1 × 1,024 + 0 × 512 + 1 × 256 + 1 × 128 + 1 × 64 + 1 × 32 + 1 × 16 + 0 × 8 + 0 × 4 + 0 × 2 + 1 × 1 = 1,521
Octal
2 7 6 1
2 × 512 + 7 × 64 + 6 × 8 + 1 × 1 = 1,521
Hexadecimal
5 f 1
5 × 256 + f × 16 + 1 × 1 = 1,521
Read as powers of two: 1,024 + 256 + 128 + 64 + 32 + 16 + 1 = 1,521.
In historical numeral systems
Egyptian
1 lotus, 5 coils of rope, 2 hobbles, 1 stroke
1 × 1,000 + 5 × 100 + 2 × 10 + 1 × 1 = 1,521. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
2 corner wedges + 5 vertical wedges (sixties place), 2 corner wedges + 1 vertical wedge (units place)
25 × 60 + 21 = 1521. Places are separated by a space on the tablet, with the higher place written first.
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
- Happy number
- Powerful number
- Harshad (Niven) number
Related numbers & connections
1521 is a year in the 16th century, in the 1520s.
Numbers Around Us
- appears inHistorical years
why?
Strength 0.50, confidence "high".
- appears alongside1433
why?
Strength 0.50, confidence "high".
History
In 1521, Tenochtitlan fell to Cortes and his allied city-states after a siege (Mesoamerica).
DocumentedHistoryGeography: MesoamericaPeriod: 1521In 1521, Luther refused to recant at the Diet of Worms and was placed under imperial ban (Central Europe).
DocumentedHistoryGeography: Central EuropePeriod: 1521
Technology & computing
With 3306, 5432 and 1433, Oracle's 1521 completes the set of database ports scanning tools check by default. Oracle's listener historically disclosed version and service information before authentication, making an exposed port useful to an attacker before any login was attempted.
DocumentedTechnology & computing
Common questions
Is 1521 a prime number?
No, 1521 is not prime.
What are the factors of 1521?
The factors of 1521 are 1, 3, 9, 13, 39, 117, 169, 507, 1521.
What is 1521 in Roman numerals?
1521 in Roman numerals is MDXXI.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 3 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 15 July 2026