| Nominal | 11991 |
| Cardinal | eleven thousand nine hundred ninety-one |
Cardinal eleven thousand nine hundred ninety-one | |
| Ordinal | 11,991st |
| Number of digits | 5 |
| Sum of digits | 21 |
| Product of digits | 81 |
| Number parity | Odd |
| Prime factorization | 3 x 7 x 571 |
| Prime factors | 3, 7, 571 |
| Number of distinct prime factors ω(n) | 3 |
| Total number of prime factors Ω(n) | 3 |
| Sum of prime factors | 581 |
| Product of prime factors | 11991 |
| Is 11991 a prime number? | No |
| Is 11991 a semiprime number? | No |
| Is 11991 a Chen prime number? | No |
| Is 11991 a Mersenne prime number? | No |
| Is 11991 a Catalan number? | No |
| Is 11991 a Fibonacci number? | No |
| Is 11991 a Idoneal number? | No |
| Square of 11991 (n2) | 143784081 |
| Cube of 11991 (n3) | 1724114915271 |
| Square root of 11991 | 109.50342460398 |
| Natural Logarithm (ln) of 11991 | 9.3919116473794 |
| Decimal Logarithm (log) of 11991 | 4.0788554029798 |
| Sine of 11991 | 0.44319414780822 |
| Cosecant of 11991 | 2.2563474832541 |
| Cosine of 11991 | -0.8964256507645 |
| Secant of 11991 | -1.1155414831639 |
| Tangent of 11991 | -0.49440145697554 |
| Cotangent of 11991 | -2.0226477610269 |
| The spelling of 11991 in words is "eleven thousand nine hundred ninety-one", meaning that: |
| 11991 is not an aban number (as it contains the letter a) |
| 11991 is not an eban number (as it contains the letter e) |
| 11991 is not an iban number (as it contains the letter i) |
| 11991 is not an oban number (as it contains the letter o) |
| 11991 is not a tban number (as it contains the letter t) |
| 11991 is not an uban number (as it contains the letter u) |
| Bengali numerals | ১১৯৯১ |
| Eastern Arabic numerals | ١١٬٩٩١ |
| Hieroglyphs numeralsused in Ancient Egypt | 𓂭𓆼𓍪𓎎𓏺 |
| Khmer numerals | ១១៩៩១ |
| Japanese numerals | 一万千九百九十一 |
| Roman numerals | n/a |
| Thai numerals | ๑๑๙๙๑ |
| Arabic | إحدى عشر ألف و تسعة مائة و واحد و تسعون |
| Croatian | jedanaest tisuća devetsto devedeset i jedan |
| Czech | jedenáct tisíc devět set devadesát jeden |
| Danish | elleve tusinde ni hundrede en og halvfems |
| Dutch | elfduizend negenhonderdéénennegentig |
| Estonian | akpe wuiɖekɛ alafa asieke blaasieke vɔ ɖekɛ |
| Faroese | ellivu tusin og níggjuhundraðognítiein |
| Filipino | labíng-isáng libó’t siyám na daán at siyám na pû’t isá |
| Finnish | yksitoistatuhattayhdeksänsataayhdeksänkymmentäyksi |
| French | onze mille neuf cent quatre-vingt-onze |
| Greek | έντεκα χίλιάδες εννιακόσια εννενήντα ένα |
| German | elftausendneunhunderteinundneunzig |
| Hebrew | אחד עשר אלף תשע מאות תשעים ואחת |
| Hindi | ग्यारह हज़ार नौ सौ इक्यानबे |
| Hungarian | tizenegyezerkilencszázkilencvenegy |
| Icelandic | ellefu þúsund og níuhundrað og níutíu og einn |
| Indonesian | sebelas ribu sembilan ratus sembilan puluh satu |
| Italian | undicimilanovecentonovantuno |
| Japanese | 一万千九百九十一 |
| Korean | 만 천구백구십일 |
| Latvian | vienpadsmit tūkstoši deviņsimt deviņdesmit viens |
| Lithuanian | vienuolika tūkstančių devyni šimtai devyniasdešimt vienas |
| Norwegian | elleve tusen ni hundre og nittién |
| Persian | یازده هزار و نهصد و نود و یک |
| Polish | jedenaście tysięcy dziewięćset dziewięćdziesiąt jeden |
| Portuguese | onze mil novecentos e noventa e um |
| Romanian | unsprezece mii nouă sute nouăzeci şi unu |
| Russian | одиннадцать тысяч девятьсот девяносто один |
| Serbian | једанаест хиљада деветсто деведесет и један |
| Slovak | jedenásť tisíc deväťsto deväťdesiatjeden |
| Slovene | enajst tisuću devetsto devetdeset ena |
| Spanish | once mil novecientos noventa y uno |
| Swahili | elfu kumi na moja, mia tisa na tisini na moja |
| Swedish | elvatusenniohundranittioen |
| Thai | หนึ่งหมื่นหนึ่งพันเก้าร้อยเก้าสิบเอ็ด |
| Turkish | on bir bin dokuz yüz doksan bir |
| Ukrainian | одинадцять тисяч девʼятсот девʼяносто один |
| Vietnamese | mười một nghìn chín trăm chín mươi mốt |
| Number 11991 reversed | 19911 | |
| Unicode Character | U+2ED7 | ⻗ |
| Unix Timestamp | Thu, 01 Jan 1970 03:19:51 +0000 | |