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.
Same number, different meanings
How 1321 is understood across different contexts — never implying one meaning because of another.
- Mathematics
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.
- History
In 1321, Dante died shortly after completing the Divine Comedy, whose three canticles of thirty-three cantos each set the vernacular on equal terms with Latin (Italy).
- 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.
1321 is part of
Factors & digit properties
- Divisors (2)
- 1, 1321
- Prime factorisation
- 1321
- Digit sum
- 7
- Digital root
- 7
Representations
- Decimal
- 1321
- Scientific notation
- 1.321 × 10^3
Roman numerals
M C C C X X I
Binary
1 0 1 0 0 1 0 1 0 0 1
1 × 1,024 + 0 × 512 + 1 × 256 + 0 × 128 + 0 × 64 + 1 × 32 + 0 × 16 + 1 × 8 + 0 × 4 + 0 × 2 + 1 × 1 = 1,321
Octal
2 4 5 1
2 × 512 + 4 × 64 + 5 × 8 + 1 × 1 = 1,321
Hexadecimal
5 2 9
5 × 256 + 2 × 16 + 9 × 1 = 1,321
Read as powers of two: 1,024 + 256 + 32 + 8 + 1 = 1,321.
In historical numeral systems
Egyptian
1 lotus, 3 coils of rope, 2 hobbles, 1 stroke
1 × 1,000 + 3 × 100 + 2 × 10 + 1 × 1 = 1,321. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
2 corner wedges + 2 vertical wedges (sixties place), 1 vertical wedge (units place)
22 × 60 + 1 = 1321. 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
- Twin prime
Related numbers & connections
1321 is a year in the 14th century, in the 1320s.
HMAC exists because prepending a key to a hash is broken by length extension, which affects MD5 and SHA-1 alike.
View 2104 →History
In 1321, Dante died shortly after completing the Divine Comedy, whose three canticles of thirty-three cantos each set the vernacular on equal terms with Latin (Italy).
DocumentedHistoryGeography: ItalyPeriod: 1321
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: 3 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 15 July 2026