646
ISO 646 is the international standard that ASCII is a variant of.
- Even
- Composite
Where 646 fits
Why 646 is special
National variants replaced characters like backslash and braces with accented letters, which is why early C code was sometimes unwritable on European terminals and why trigraph escapes exist in the language.
646 is part of
Factors & digit properties
- Divisors (8)
- 1, 2, 17, 19, 34, 38, 323, 646
- Prime factorisation
- 2 × 17 × 19
- Digit sum
- 16
- Digital root
- 7
Representations
- Decimal
- 646
- Binary
- 1010000110
- Octal
- 1206
- Hexadecimal
- 286
- Roman numeral
- DCXLVI
- Scientific notation
- 6.460 × 10^2
Other mathematical patterns
- Palindromic number
- Deficient number
Related numbers & connections
ISO 646 defined national variants of a seven-bit set and ISO 8859 extended to eight bits with sixteen incompatible parts. Both problems were ended by Unicode.
View 8859 →Other connections
- developed from8859
why?
Strength 0.50, confidence "high".
Technology & computing
National ISO 646 variants substituted accented letters for braces and backslashes, making standard C source impossible to type on some terminals. Trigraphs were added to the language purely to work around it.
DocumentedTechnology & computing
Common questions
Is 646 a prime number?
No, 646 is not prime.
What are the factors of 646?
The factors of 646 are 1, 2, 17, 19, 34, 38, 323, 646.
What is 646 in Roman numerals?
646 in Roman numerals is DCXLVI.
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