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 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
- Binary
- 10111110001
- Octal
- 2761
- Hexadecimal
- 5f1
- Roman numeral
- MDXXI
- Scientific notation
- 1.521 × 10^3
Other mathematical patterns
- Deficient number
- Happy number
- Powerful number
- Harshad (Niven) number
Related numbers & connections
Oracle and SQL Server defaults. With MySQL's 3306 and PostgreSQL's 5432 they are the four ports database scanning tools try first, because the defaults are almost never changed.
View 1433 →Numbers Around Us
- appears alongside1433
why?
Strength 0.50, confidence "high".
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: 1 reviewer-confirmed record, sourced and reviewed before publication.
Last reviewed: 3 August 2026