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11 (eleven) is a positive integer following 10 and preceding 12. Its ordinal form is written "11th" or "eleventh".

## Properties

• 11 is an odd prime number.
• 11 is the first number which cannot be counted with a human's ten fingers, using each finger as a tally mark. In English, it is the smallest positive integer requiring three syllables and the largest prime number with a single-morpheme name. Its etymology originates from a Germanic compound ainlif meaning "one left".[1]
• 11 is the smallest non-trivial repdigit. Multiples of it up through 99 are also repdigits. 11 is a the first repunit number.
• 11 is also equal to $$n(2)$$ in the block subsequence theorem.
• 11 is the largest known number n such that 2^n contains only even decimal digits. The decimal expansion of 2^11 is 2048, which contains all even digits. 2^n for all 11<n<1000000 contains at least one odd digit.

## In googology

• In Greek-based number naming systems, 11 is associated with prefix "endeka-", and with prefix "undeci-" in Latin systems.
• Wiki user Denis Maksudov coined the name zeralum for this number, and it's equal to $$f_0(10)$$ using the fast-growing hierarchy.[2] This name belongs to the Alpha series.
• In duodecimal, the digit eleven is normally represented by an upside-down 3 and is named "el".

## In popular culture

• The phrase "oh yeah" is spoken 11 times in the hit Yello song "Oh Yeah".

## Sources

Numbers by Denis Maksudov
Alpha series
Epsilon series
Epsilon(0)-multiplication series: Bultep · Trultep · Quadrultep · Quintultep · Sextultep · Septultep · Octultep · Nonultep · Dekultep · Hektultep · Kilultep · Megultep · Gigultep · Terultep · Petultep · Exultep · Zettultep · Yottultep
Epsilon(0)-exponentiation series: Bexep · Trexep · Quadrexep · Quintexep · Sextexep · Septexep · Octexep · Nonexep · Dekexep · Hektexep · Kilexep · Megexep · Gigexep · Terexep · Petexep · Exexep · Zettexep · Yottexep
Epsilon(0)-tetration series: Bitetrep · Tritetrep · Quadritetrep · Quintitetrep · Sextitetrep · Septitetrep · Octitetrep · Nonitetrep · Dekotetrep · Hektotetrep · Kilotetrep · Megotetrep · Gigotetrep · Terotetrep · Petotetrep · Exotetrep · Zettotetrep · Yottotetrep
Inserted epsilon series: Uninep · Binep · Trinep · Quadrinep · Quintinep · Sextinep · Septinep · Octinep · Noninep · Dekinep · Hektinep · Kilinep · Meginep · Giginep · Terinep · Petinep · Exinep · Zettinep · Yottinep
Inserted zeta series
Inserted eta series
Phi series
Inserted gamma series
Theta series
Psi series
$$I_\alpha$$ series
$$I(\alpha,\beta)$$ series
Initial $$I(\alpha,\beta)$$ series: Unimah · Bimah · Trimah · Quadrimah · Quintimah · Sextimah · Septimah · Octimah · Nonimah · Dekimah · Hektimah · Kilimah · Megimah · Gigimah · Terimah · Petimah · Eximah · Zettimah · Yottimah
Inserted $$I(\alpha,\beta)$$ series: Uninimah · Binimah · Trinimah · Quadrinimah · Quintinimah · Sextinimah · Septinimah · Octinimah · Noninimah · Dekinimah · Hektinimah · Kilinimah · Meginimah · Giginimah · Terinimah · Petinimah · Exinimah · Zettinimah · Yottinimah
M-series