2 | |||||||||
---|---|---|---|---|---|---|---|---|---|
Numbers 0 - 99 | |||||||||
0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 |
20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 |
30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 |
40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 |
50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 |
60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 |
70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 |
80 | 81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 |
90 | 91 | 92 | 93 | 94 | 95 | 96 | 97 | 98 | 99 |
2 (two) is a positive integer following 1 and preceding 3. Its ordinal form is written "second" or "2nd".
Properties
2 is even, and a prime number — the only number with both of those properties. (An old joke states that this makes 2 the oddest prime of all.)
Since 10 is a multiple of 2, a number written in base 10 can be easily be tested for evenness by looking at the last decimal digit. Even numbers always end in 0, 2, 4, 6, or 8.
2 is the only even prime number.
In googology
Calling any standard hyperoperation (addition, multiplication, exponentiation, tetration, etc.) with 2 as both of its arguments will always result in 4. BEAF arrays using 2 as a base tend to become degenerate and evaluate to 4: {2, 2 (1) 2} = {2, 2} = 22 = 4. For this reason, Bowers often coins googologisms based on the number 3, which do not become degenerate.
In Greek-based number naming systems, 2 is associated with prefix di-, and with prefix duo- in Latin systems.
Using Sbiis Saibian's naming system, this number is called clover mite-crumb.[1]
Aarex Tiaokhiao calls this number binary-uoonol.[2]
Username5243 calls this number Binary-Goonol, and it's equal to 2[1]1 in Username5243's Array Notation.[3]
Googological functions returning 2
- Simple subcubic graph numbers: \(\text{SSCG}(0) = 2\)
- Xi function: \(\Xi(2)=2\)
- Laver table: \(q(1)=2\)
- Exploding Tree function: \(E(2)=2\)
- Latin square: \(L(2)=2\)
- Weak tree function: \(\text{tree}(1)=2\)
As a cash denomination
Some currencies, such as the Ghanaian cedi and the United States dollar, have banknotes with this number in the denomination.
Some currencies, such as the euro and the pound sterling, have coins with this number in the denomination.
Sources
See also
Dust mite group: dust mite-speck · dust mite-crumb · dust mite-chunk · (binary/ternary/octal)dust mite · dust mite-bunch · dust mite-crowd · dust mite-swarm
Cheese mite group: cheese mite-speck · cheese mite-crumb · cheese mite-chunk · (binary/ternary/octal)cheese mite · cheese mite-bunch · cheese mite-crowd · cheese mite-swarm
Clover mite group: clover mite-speck · clover mite-crumb · clover mite-chunk · (binary/ternary/octal)clover mite · clover mite-bunch · clover mite-crowd · clover mite-swarm
Pipsqueak group: (binary/ternary/octal)pipsqueak
Little squeaker group: (binary/ternary/octal)little squeaker
Small fry group: (binary/ternary/octal)small fry
Guppy group: (binary/ternary/octal)guppyspeck · (binary/ternary/octal)guppycrumb · (binary/ternary/octal)guppychunk · (ternary/quaternary/quinary/duodecimal/hexadecimal/vigesimal/sexagesimal)guppy(bit/byte)
Minnow group: (binary/ternary/octal)minnowspeck · (binary/ternary/octal)minnowcrumb · (binary/ternary/octal)minnowchunk · (ternary)minnow(bit/byte)
Goby group: (binary/ternary/octal)gobyspeck · (binary/ternary/octal)gobycrumb · (binary/ternary/octal)gobychunk · (ternary)goby(bit/byte)
Gogol group: (binary/ternary/octal)gogolspeck · (binary/ternary/octal)gogolcrumb · (binary/ternary/octal)gogolchunk · (ternary/quadternary/quinary/duodecimal/hexadecimal/vigesimal/sexagesimal)gogol(bit/byte)
Jumbo shrimp group: (binary/ternary/octal)jumbo shrimp
Lightweight group: (binary/ternary/octal)lightweight
Ogol group: (binary/ternary/octal)ogolspeck · (binary/ternary/octal)ogolcrumb · (binary/ternary/octal)ogolchunk · (ternary/quaternary/quinary/duodecimal/hexadecimal/vigesimal/sexagesimal)ogol(bit/byte)
Tiny twerpuloid group: (binary/ternary/octal)tiny twerpuloid
Googol group: (binary/ternary/octal)googolspeck · (binary/ternary/octal)googolcrumb · (binary/ternary/octal)googolchunk · (ternary/quaternary/quinary/duodecimal/hexadecimal/vigesimal/sexagesimal)googol*(bit/byte) · googolbunch · googolcrowd · googolswarm
Eceton group: ecetonspeck · ecetoncrumb · ecetonchunk · ecetonbunch · ecetoncrowd · ecetonswarm
*Not Saibian's
-chime group: (binary/octal)guppychime · (binary/octal)gogolchime · ogolchime · (binary/octal)googolchime · ecetonchime
-bell group: guppybell · gogolbell · ogolbell · googolbell · ecetonbell
-toll group: guppytoll · gogoltoll · ogoltoll · googoltoll · ecetontoll
-gong group: guppygong · gogolgong · ogolgong · googolgong · ecetongong
-bong group: guppybong · gogolbong · ogolbong · googolbong · ecetonbong
-throng group: guppythrong · gogolthrong · ogolthrong · googolthrong · ecetonthrong
-gandingan group: guppygandingan · gogolgandingan · ogolgandingan · googolgandingan · ecetongandingan
Higher googol-n-gongs: googolquintigong · googolsextigong · googolseptigong · googoloctigong · googolnonigong · googoldecigong · googol-undecigong · googol-duodecigong · googol-tredecigong · googol-quattuordecigong · googol-quindecigong · googol-sexdecigong · googol-septendecigong · googol-octodecigong · googol-novemdecigong · googolvigintigong · googoltrigintigong · googolquadragintigong · googolquinquagintigong · googolsexagintigong · googolseptuagintigong · googoloctogintigong · googolnonagintigong · googolcentigong · googolmilligong · googolmilli-milligong
-duplex group: milliduplexion · billiduplexion · trilliduplexion · guppyduplex · googolduplexibit · gogolduplex · googolduplexibyte · ecetonduplex · googolduplexichime · googolduplexitoll · googolduplexigong · googolduplexibong · googolduplexithrong
-triplex group: millitriplexion · billitriplexion · trillitriplexion · guppytriplex · googoltriplexibit · gogoltriplex · googoltriplexibyte · ecetontriplex · googoltriplexichime · googoltriplexitoll · googoltriplexigong · googoltriplexithrong
-quadriplex group: guppyquadriplex · googolquadriplexibit · gogolquadriplex · googolquadriplexibyte · ecetonquadriplex · googolquadriplexichime · googolquadriplexitoll · googolquadriplexigong
-quintiplex group: guppyquintiplex · googolquintiplexibit · gogolquintiplex · googolquintiplexibyte · ecetonquintiplex · googolquintiplexichime · googolquintiplexitoll · googolquintiplexigong
-sextiplex group: guppysextiplex · googolsextiplexibit · gogolsextiplex · googolsextiplexibyte · ecetonsextiplex · googolsextiplexichime · googolsextiplexitoll · googolsextiplexigong
-septiplex group: guppyseptiplex · googolseptiplexibit · gogolseptiplex · googolseptiplexibyte · ecetonseptiplex · googolseptiplexichime · googolseptiplexitoll · googolseptiplexigong
-octiplex group: guppyoctiplex · googoloctiplexibit · gogoloctiplex · googoloctiplexibyte · ecetonoctiplex · googoloctiplexichime · googoloctiplexitoll · googoloctiplexigong
-noniplex group: guppynoniplex · googolnoniplexibit · gogolnoniplex · googolnoniplexibyte · ecetonnoniplex · googolnoniplexichime · googolnoniplexitoll · googolnoniplexigong
-deciplex group: guppydeciplex · googoldeciplexibit · gogoldeciplex · googoldeciplexibyte · ecetondeciplex · googoldeciplexichime · googoldeciplexitoll · googoldeciplexigong · googoldeciplexibong · googoldeciplexithrong
-vigintiplex group: guppyvigintiplex · googolvigintiplexibit · gogolvigintiplex · googolvigintiplexibyte · eceton-vigintiplex · googolvigintiplexichime · googolvigintiplexitoll · googolvigintiplexigong
-trigintiplex group: guppytrigintiplex · googoltrigintiplexibit · gogoltrigintiplex · googoltrigintiplexibyte · eceton-trigintiplex · googoltrigintiplexichime · googoltrigintiplexitoll · googoltrigintiplexigong
-quadragintiplex group: guppyquadragintiplex · googolquadragintiplexibit · gogolquadragintiplex · googolquadragintiplexibyte · eceton-quadragintiplex · googolquadragintiplexichime · googolquadragintiplexitoll · googolquadragintiplexigong
-quinquagintiplex group: guppyquinquagintiplex · googolquinquagintiplexibit · gogolquinquagintiplex · googolquinquagintiplexibyte · eceton-quinquagintiplex · googolquinquagintiplexichime · googolquinquagintiplexitoll · googolquinquagintiplexigong
-sexagintiplex group: guppysexagintiplex · googolsexagintiplexibit · gogolsexagintiplex · googolsexagintiplexibyte · eceton-sexagintiplex · googolsexagintiplexichime · googolsexagintiplexitoll · googolsexagintiplexigong
-septuagintiplex group: guppyseptuagintiplex · googolseptuagintiplexibit · gogolseptuagintiplex · googolseptuagintiplexibyte · eceton-septuagintiplex · googolseptuagintiplexichime · googolseptuagintiplexitoll · googolseptuagintiplexigong
-octogintiplex group: guppyoctogintiplex · googoloctogintiplexibit · gogoloctogintiplex · googoloctogintiplexibyte · eceton-octogintiplex · googoloctogintiplexichime · googoloctogintiplexitoll · googoloctogintiplexigong
-nonagintiplex group: guppynonagintiplex · googolnonagintiplexibit · gogolnonagintiplex · googolnonagintiplexibyte · eceton-nonagintiplex · googolnonagintiplexichime · googolnonagintiplexitoll · googolnonagintiplexigong
-centiplex group: guppycentiplex · googolcentiplexibit · gogolcentiplex · googolcentiplexibyte · eceton-centiplex · googolcentiplexichime · googolcentiplexitoll · googolcentiplexigong · googolcentiplexibong · googolcentiplexithrong
-milliplex group: guppymilliplex · googolmilliplexibit · gogolmilliplex · googolmilliplexibyte · eceton-milliplex · googolmilliplexichime · googolmilliplexitoll · googolmilliplexigong · googolmilliplexibong · googolmilliplexithrong
-milli-milliplex group: guppymilli-milliplex · googolmilli-milliplexibit · gogolmilli-milliplex · googolmilli-milliplexibyte · eceton-millimilliplex · googolmillimilliplexichime · googolmillimilliplexitoll · googolmillimilliplexigong · googolmillimilliplexibong · googolmillimilliplexithrong
Megoogol · Meg-Googol · Meg-Doogol · Meg-Kiloogol · Meg-Kil-Googol · Meg-Dukiloogol · Meg-Trukiloogol · Dumegoogol · Dumeg-Googol · Dumeg-Kiloogol · Dumeg-Dukiloogol · Trumegoogol · Trumeg-Kiloogol · Tetrumegoogol · Pentumegoogol · Gigoogol · Gig-Googol · Gig-Kiloogol · Gig-Megoogol · Dugigoogol · Trugigoogol · Teroogol · Duteroogol · Truteroogol · Petoogol · Ectoogol · Zettoogol · Yottoogol · Xennoogol · Wekoogol
Note: The readers should be careful that numbers defined by Username5243's Array Notation are ill-defined as explained in Username5243's Array Notation#Issues. So, when an article refers to a number defined by the notation, it actually refers to an intended value, not an actual value itself (for example, a[c]b = \(a \uparrow^c b\) in arrow notation). In addition, even if the notation is ill-defined, a class category should be based on an intended value when listed, not an actual value itself, as it is not hard to fix all the issues from the original definition, hence it should not be removed.