2

2 (two) is a number, numeral and digit. It is the natural number following 1 and preceding 3. It is the smallest and the only even
prime number.

Because it forms the basis of a duality, it has religious and spiritual significance in many cultures.

As a word

Two is most commonly a determiner used with plural countable nouns, as in two days or I'll take these two.[1] Two is a noun when it
refers to the number two as in two plus two is four.

Etymology of two

The word two is derived from the Old English words twā (feminine), tū (neuter), and twēġen (masculine, which survives today in the
form twain).[2]

The pronunciation /tuː/, like that of who is due to the labialization of the vowel by the w, which then disappeared before the related
sound. The successive stages of pronunciation for the Old English twā would thus be /twɑː/, /twɔː/, /twoː/, /twuː/, and finally
/tuː/.[2]

Mathematics

An integer is determined to be even if it is divisible by two. When written in base 10, all multiples of 2 will end in 0, 2, 4, 6, or 8.[3] 2 is
the smallest and the only even prime number, and the first Ramanujan prime.[4] It is also the first superior highly composite
number,[5] and the first colossally abundant number.[6]

Geometry

A digon is a polygon with two sides (or edges) and two vertices.[7]: 52 Two distinct points in a plane are always sufficient to define a
unique line in a nontrivial Euclidean space.[8]

Set theory

A set that is a field has a minimum of two elements.[9] A Cantor space is a topological space homeomorphic to the Cantor set.

Base 2

Binary is a number system with a base of two, it is used extensively in computing.[10]

List of basic calculations

Multiplication 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 50 100

2×x 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 100 200

Division 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

2÷x 2 0.6 0.5 0.4 0.3 0.285714 0.25 0.2 0.2 0.18 0.16 0.153846 0.142857 0.13 0.125 0.1176470588235294 0.1 0.105263157894736842 0.1
1
x÷2 0.5 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10
 ←1 2 3→

−1 0 1 2 3 4 5 6 7 8 9 →
List of numbers · Integers
← 0 10 20 30 40 50 60 70 80 90 →

Cardinal two

Ordinal 2nd (second)

Numeral system binary

Factorization prime

Gaussian integer
factorization

Prime 1st

Divisors 1, 2

Greek numeral Β´

Roman numeral II, ii

Greek prefix di-

Latin prefix duo-/bi-

Old English prefix twi-

Binary 102

Ternary 23

Senary 26

Octal 28

Duodecimal 212

Hexadecimal 216

Greek numeral β'

Arabic, Kurdish, ٢
Persian, Sindhi, Urdu

Ge'ez ፪
Bengali ২
Chinese numeral 二，弍，貳
Devanāgarī २
Telugu ౨
Tamil ௨
Kannada ೨
Hebrew ‫ב‬
Armenian Բ
Khmer ២
Maya numerals ••

Thai ๒

Georgian Ⴁ/ⴁ/ბ(Bani)
Malayalam ൨
Babylonian numeral 𒐖

Egyptian hieroglyph, ||
Aegean numeral,
Chinese counting rod

Morse code .._ _ _

 Exponentiation 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

2x 2 8 32 64 128 256 512 1024 2048 4096 8192 16384 32768 65536 131072 262144 524288 1048576
4 16
x2 1 9 25 36 49 64 81 100 121 144 169 196 225 256 289 324 361 400

Evolution of the Arabic digit

The digit used in the modern Western world to represent the number 2 traces its roots back to the
Indic Brahmic script, where "2" was written as two horizontal lines. The modern Chinese and
Japanese languages (and Korean Hanja) still use this method. The Gupta script rotated the two lines
45 degrees, making them diagonal. The top line was sometimes also shortened and had its bottom end curve towards the center
of the bottom line. In the Nagari script, the top line was written more like a curve connecting to the bottom line. In the Arabic
Ghubar writing, the bottom line was completely vertical, and the digit looked like a dotless closing question mark. Restoring the
bottom line to its original horizontal position, but keeping the top line as a curve that connects to the bottom line leads to our
modern digit.[11]

In fonts with text figures, digit 2 usually is of x-height, for example, .

In science

The first magic number.[12]

See also

Binary number

References

1. Huddleston, Rodney D.; Pullum, Geoffrey K.; Reynolds, Brett 6. "A004490 - OEIS" (https://oeis.org/A004490) . oeis.org.
(2022). A student's introduction to English grammar (https:// Retrieved 2024-11-28.
www.worldcat.org/oclc/1255524478) (2nd ed.).
7. Wilson, Robin (2014). Four Colors Suffice (Revised
Cambridge, United Kingdom: Cambridge University Press.
color ed.). Princeton University Press. ISBN 978-0-691-
p. 117. ISBN 978-1-316-51464-1. OCLC 1255524478 (http
15822-8.
s://search.worldcat.org/oclc/1255524478) .
8. Carrell, Jim. "Chapter 1 | Euclidean Spaces and Their
2. "two, adj., n., and adv." (https://www.oed.com/search/dictio
Geometry". MATH 307 Applied Linear Algebra (https://perso
nary/?q=two%2C+adj.%2C+n.%2C+and+adv.) . Oxford
nal.math.ubc.ca/~carrell/307_chap1.pdf) (PDF).
English Dictionary (Online ed.). Oxford University Press.
(Subscription or participating institution membership (https:// 9. "Field Contains at least 2 Elements" (https://proofwiki.org/

www.oed.com/public/login/loggingin#withyourlibrary) wiki/Field_Contains_at_least_2_Elements) .

required.) 10. "How computers see the world - Binary - KS3 Computer
3. Sloane, N. J. A. (ed.). "Sequence A005843 (The Science Revision" (https://www.bbc.co.uk/bitesize/guides/

nonnegative even numbers)" (https://oeis.org/A005843) . z26rcdm/revision/1) . BBC Bitesize. Retrieved 2024-06-05.

The On-Line Encyclopedia of Integer Sequences. OEIS 11. Georges Ifrah, The Universal History of Numbers: From
Foundation. Retrieved 2022-12-15. Prehistory to the Invention of the Computer transl. David

4. "Sloane's A104272 : Ramanujan primes" (https://web.archi Bellos et al. London: The Harvill Press (1998): 393, Fig.
ve.org/web/20110428165633/https://oeis.org/A10427 24.62

2) . The On-Line Encyclopedia of Integer Sequences. OEIS

Foundation. Archived from the original (https://oeis.org/A1
04272) on 2011-04-28. Retrieved 2016-06-01.

5. "A002201 - OEIS" (https://oeis.org/A002201) . oeis.org.

Retrieved 2024-11-28.
12. "The Complete Explanation of the Nuclear Magic Numbers
Which Indicate the Filling of Nucleonic Shells and the
Revelation of Special Numbers Indicating the Filling of
Subshells Within Those Shells" (https://web.archive.org/we
b/20191202130317/http://www.sjsu.edu/faculty/watkins/
magicnumbers2.htm) . www.sjsu.edu. Archived from the
original (https://www.sjsu.edu/faculty/watkins/magicnum
bers2.htm) on 2019-12-02. Retrieved 2019-12-22.

External links

Prime curiosities: 2 (http://primes.utm.edu/curios/page.php/2.html)

Mathematics portal