Four (number)

4

-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 →

four

4th
(fourth)

2²

1, 2, 4

Δ´

IV

Roman numeral (unicode)

Ⅳ, ⅳ

/

100₂

11₃

10₄

4₅

4₆

4₈

4₁₂

4₁₆

4₂₀

4₃₆

δ (or Δ)

Arabic, Saraiki & Kurdish

٤

۴

፬

৪

Chinese numeral

四，亖，肆

넷,사

४

౪

൪

௪

ד

៤

๔

४

၄

4 (four; /fɔːr/) is a number, numeral, and glyph. It is the natural number following 3 and preceding 5.

Four is the smallest composite number, its proper divisors being 1 and 2.

4 is the smallest squared prime (p²) and the only even number in this form. 4 is also the only square one more than a prime number.

A number is a multiple of 4 if its last two digits are a multiple of 4. For example, 1092 is a multiple of 4 because 92 = 4 × 23.

In addition, 2 + 2 = 2 × 2 = 2² = 4. Continuing the pattern in Knuth's up-arrow notation, 2 ↑↑ 2 = 2 ↑↑↑ 2 = 4, and so on, for any number of up arrows. (That is, 2 [n] 2 = 4 for every positive integer n, where a [n] b is the hyperoperation.)

A four-sided plane figure is a quadrilateral (quadrangle) which include kites, rhombi, rectangles and squares, sometimes also called a tetragon. A circle divided by 4 makes right angles and four quadrants. Because of it, four (4) is the base number of the plane (mathematics). Four cardinal directions, four seasons, the duodecimal system, and the vigesimal system are based on four.

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