ExtraBase - by Le Nogueira

3 is the only prime 1 less than a perfect square. - Robin Regan
is the number of spatial dimensions needed to mathematically describe a solid.
are the primary colors.
are the geometric constructions you cannot build using just a ruler and compasses: 1. You cannot trisect - divide into three equal parts - a given angle; 2. Double a cube; and 3. Square a circle.
A number is divisible by 3 when the sum of its digits can be divided by 3.
If the denominator of a rational number is not divisible by 3, then the repeating part of its decimal expansion is an integer divisible by 9. Example: 1/7 = 0.142857... has a repeating part '142857' divisible by 9. Another example with a larger recurring decimal: 1/23 = 0.0434782608695652173913... has a repeating part '0434782608695652173913' divisible by 9.
3 + 2 = log₂ 32
= (14 - 65) + 5 (sum of two square roots)
= 4! / (4 x 4)
= XV/V = CL/L = MD/D
= 4 + 4 – 5 = 4³ + 4³ – 5³
= 17,469 / 5,823 (this division contains all digits 1 through 9 once)
3 x 51249876 = 153749628 (the multiplication uses all 9 digits once - and so does its product!)
3 x 37 = 111
33 x 3367 = 111,111
333 x 333667 = 111,111,111
3333 x 33336667 = 111,111,111,111
33333 x 3333366667 = 111,111,111,111,111
3 x 1.5 = 3 + 1.5
3² = 3! + 3
3² = 5² - 4²
3³ = 6³ - 5³ - 4³
3³ = 3² + 3² + 3²
3⁴ x 425 = 34425
3 is the minimum colors needed to create camouflage patches, usually used in military compounds and vehicles. - posted by George Pantazis
A 3 x 3 alphamagic square is a magic square for which the number of letters in the word for each number generates another magic square, for instance:

5 22 18 28 15 2 12 8 25

five (4) twenty-two (9) eighteen (8) twenty-eight (11) fifteen (7) two (3) twelve (6) eight (5) twenty-five (10)

A 3 x 6 rectangle has an area equal to its perimeter.
In one gram of water the number of molecules is about:
3.3 x 10²² = 33000000000000000000000
The balanced ternary base, is a numeral system which uses 3 values or digits: -1, 0, and 1. It works as follows (in the example, the symbol 1 denotes the digit -1):

Decimal	-6	-5	-4	-3	-2	-1	0	1	2	3	4	5	6	7
Balanced ternary	110	111	11	10	11	1	0	1	11	10	11	111	110	111

Ternary or base-3 numbers can be converted to balanced ternary notation by adding 1111... with carry, then subtracting 1111... without borrow. For instance:
021₃ + 111₃ = 202₃, 202₃ - 111₃ = 111_3(bal) = 7₁₀
This non-standard positional numeral system is easily represented as electronic signals, as potential can either be negative, neutral, or positive (comparison logic). The balance ternary system is also useful to solve the classical 2-pan balance puzzle.
The letters A, F, H, K, N, Y and Z are made up with 3 lines.
In SMS language <3 font=""> means 'I love you', and <333 font="">, 'I love you so much'.
3 hundred millions of Indians live with less than 1 dollar per day (2004).
Non-paternity rates: statistically, one in three men who ask for paternity test turn out not to be the biological parent.
An octopus has 3 hearts.
The number 3 symbolizes the principle of growth. In Guangdong province, China, three is associated with living or giving birth.
"Sanqing" (also known as "Sanxing" or "Sancai"), in the Mystical Numbers of Taoism, represents the number 3 and symbolizes the Three Luminaries: Sun, Moon, Stars. It also defines the concept of "Heaven, Mankind, Earth" as well as "Upper, Centre, Lower".
Deep thought: "There are 3 kinds of people: those who can count and those who can't".
Riddle 1: Spell 'mousetrap' in 3 letters...
Answer: C-A-T.
Riddle 2: Spell 'water' in 3 letters...
Answer: H-2-O.
Joke: Chuck Norris once won a game of Connect Four in 3 moves!
If you’re a Simpsons fan, then you problably know about “Blinky”, the three-eyed fish found near the nuclear plant where Homer Simpson was working. As it turns out, the Simpsons were right yet again, as fishermen in Córdoba, Argentina caught a three-eyed wolf fish in a reservoir fed by a local nuclear power plan! (Fri, Oct 28, 2011)
In the taoist mythology, Erlang Shen (二郎神), or Erlang is a Chinese God with a third truth-seeing eye in the middle of his forehead.
The French sentence 'un bonhomme haut comme trois pommes' (a 3-apple-tall fellow) and the German sentence 'ein Kerlchen drei Käse hoch' (a 3-cheese-tall fellow) mean both a pint-sized guy/child.
"Les fourmis, chacune d'elles ressemble au chiffre 3. Et il y en a! Il y en a 333333333333... jusqu'à l'infini" (Jules Renard, 'Histoires naturelles').
Translation: "The ants. Each of them resembles a figure 3. That's, it. There are 333333333333 to infinity".
'Bookkeeper' and 'bookkeeping' are the only words in the English language with three consecutive double letters.
The most common three-letter words in order of frequency are: the, and, for, are, but, not, you, all, any, can, had, her, was, one, our, out, day, get, has, him, his, how, man, new, now, old, see, two, way, who, boy, did, its, let, put, say, she, too, use.
The name "Mitsubishi" (三菱) consists of two parts: "mitsu" meaning 'three' and "bishi" meaning 'water caltrop', and hence 'rhombus', which is reflected in the company's famous logo (it is also translated as 'three diamonds'). Other Japanese family names containing the number 3: Mitsudani, Mitsugi, Mitsui, Mitsuhashi, Mitsude, Mitsuishi, Mitsumura, Mitsubori, Mitsumata, Mitsuyama, Mitsuzawa, Mitsuya, Mitsukuchi, Mitsukyou, Mitsuboshi, Mitsuzima, Mitsue, Mitsuike, Mitsuaichou, Mitsubuchi, Mitsuse, Mitsuyanagi, Mitsumachi, Mitsukunugi, Mitsuwa, Mitsuzaku, Mitsumatsu, Mitsuhuzi, Mitsuduka, Mitsuwari.

THREE in different languages (© G. Sarcone) (Old English thrīe)

Indo-european | *TREYES, *TISORES, *TRI | Sanskrit | TRÎ |     trayaḥ (m) / tisraḥ (f) / trīṇi (f) Greek, Attic | TPEIΣ, TPIA  TRÊS, TRIA | Latin | TRES, TRIA |, Archaic Latin | *TREIES |

Italian tre; French trois; Spanish and Catalan tres; Provençal trei, tres; Portuguese três; Romanian trei; Romansh trais; Sardinian très.

Old Celtic | TRI |

Breton tri (m), teir (f); Welsh tri (m), tair (f); Irish trí (m), teoir (f, old Irish), triúir (people).

Old Germanic | THRIJIZ |

Dutch drie; German drei; Danish, Norwegian, and Swedish tre; Icelandic þrír.

Old Slavic | TRIJE, TRI |

Russian три tri; Czech tři; Slovenian trí; Polish trzy.

Proto Indo-Iranian | *TRAYAS |

Persian سه se; Hindi तीन t̪iːn.

Evolution from 'seal script' to modern sinograph 三 : Old Chinese (pron.) | sâm |

Chinese 三 sān. The sinograph 叁 is used as a replacement for sān on legal and financial documents to prevent fraud.

Proto-Semitic | *SALATh | Semitic root | Th-L-Th | Ancient Egyptian [ḫmt'-] khemet; Akkadian shalash; Punic shlosht.

Arabic ثلاثة thalathâ; Hebrew שלושה shlôshah; Maltese: tlieta; Amharic sost.

More languages Magyar három. Turkish üç. Mayan oxi'. Nahuatl ēyi. Suomi kolme. Zulu (ku)thathu.

HIDDEN ROOTS The roots of the word three are hidden in the following words: contest, detest, obtest, protest, sesterce, sitar, teapoy, tercet, tertian, tern, terpolymer, test, testament, testicle, testify, testimony, trammel, travel, trefoil, trench, trephine, trey, triad, triangle, triathlon, tribe, trio, triple, triplex, trine, trinity, trimurti, trivial, triumvir, trocar, troika; third, thrice. In French: travail, treillis, trémail. In Spanish: terliz, trabajo.