9999 (number)

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← 9998 9999 10000 →
Cardinal nine thousand nine hundred ninety-nine
Ordinal 9999th
(nine thousand nine hundred ninety-ninth)
Factorization 32× 11 × 101
Greek numeral ,ΘϠϞΘ´
Roman numeral MXCMXCIX or IXCMXCIX
Binary 100111000011112
Ternary 1112011003
Quaternary 21300334
Quinary 3044445
Senary 1141436
Octal 234178
Duodecimal 595312
Hexadecimal 270F16
Vigesimal 14JJ20
Base 36 7PR36

Nine thousand nine-hundred ninety-nine (9999) is the natural number following 9998 and preceding 10000.

9999 is an auspicious number in Chinese folklore. Many estimations of the rooms contained the Forbidden City point to 9999. Chinese tomb contracts often involved being buried with 9999 coins, relational notion to Joss paper, as it was believed the dead would need that amount to buy the burial plot from the Earth goddess.[1]

9999 is also the emergency telephone number in Oman.[2]


9999 can be used as a divisor to generate 4-digit decimal recurrences. For example, 1234 / 9999 = 0.123412341234... .

9999 is a Kaprekar number.[3]

Computer and software[edit]

9999 was the last possible line number in some older programming languages such as BASIC.[4] Often the line "9999 END" was the first line written for a new program.

Some very old software used "9999" as end of file, however no problems occurred September 9, 1999[5]


The King of Fighters character K9999 has the number on his name, although it is read as "kay-four-nine"


  1. ^ Valerie Hansen, Negotiating Daily Life in Traditional China: How Ordinary People Used Contracts, 600-1400 (Yale University Press, 1995)
  2. ^ (http://www.rop.gov.om/english/regionalinfo.asp)
  3. ^ "Sloane's A006886 : Kaprekar numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-03. 
  4. ^ Ordman, Edward (January 1983), "Writing Transportable BASIC Part 1", COMPUTE! (32): 26 
  5. ^ Alfred, Randy (9 September 2011). "Sept. 9, 1999: 9/9/99 No Big Deal for Computers". Wired. Wired. Archived from the original on 1 June 2014. Retrieved 19 November 2017. Conversely, at least one expert worried that the real problem wasn’t in the date being interpreted as an end-of-file marker (or trailer), but in an end-of-file marker being interpreted as a date.