1321
RFC 1321 defines the MD5 message-digest algorithm.
- Odd
- Prime
Where 1321 fits
Why 1321 is special
It is comprehensively broken for security — collisions can be produced in seconds — yet still appears everywhere as a file checksum, which is a different job.
1321 is part of
Factors & digit properties
- Divisors (2)
- 1, 1321
- Prime factorisation
- 1321
- Digit sum
- 7
- Digital root
- 7
Representations
- Decimal
- 1321
- Binary
- 10100101001
- Octal
- 2451
- Hexadecimal
- 529
- Roman numeral
- MCCCXXI
- Scientific notation
- 1.321 × 10^3
Other mathematical patterns
- Deficient number
- Twin prime
Related numbers & connections
HMAC exists because prepending a key to a hash is broken by length extension, which affects MD5 and SHA-1 alike.
View 2104 →Technology & computing
RFC 1321 specifies MD5, producing a 128-bit digest. Practical collision attacks were demonstrated from 2004, so MD5 is unsuitable for signatures or certificates while remaining common for non-adversarial integrity checks.
DocumentedTechnology & computingGeography: International — IETFPeriod: 1992CWE-1321 is improperly controlled modification of object prototype attributes, in which writing to a shared prototype changes the behaviour of objects the attacker never touched.
DocumentedTechnology & computingGeography: International — MITRE CWEPeriod: 2006–
Common questions
Is 1321 a prime number?
Yes, 1321 is prime — it has exactly two positive divisors: 1 and itself.
What are the factors of 1321?
The factors of 1321 are 1, 1321.
What is 1321 in Roman numerals?
1321 in Roman numerals is MCCCXXI.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 2 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 3 August 2026