40 (number)
| ||||
|---|---|---|---|---|
| Cardinal | forty | |||
| Ordinal | 40th (fortieth) | |||
| Numeral system | quadragesimal | |||
| Factorization | 23 × 5 | |||
| Divisors | 1, 2, 4, 5, 8, 10, 20, 40 | |||
| Greek numeral | Μ´ | |||
| Roman numeral | XL | |||
| Latin prefix | quadrage- | |||
| Binary | 1010002 | |||
| Ternary | 11113 | |||
| Octal | 508 | |||
| Duodecimal | 3412 | |||
| Hexadecimal | 2816 | |||
40 (forty) is the natural number following 39 and preceding 41.
Though the word is related to "four" (4), the spelling "forty" replaced "fourty" in the course of the 17th century[1][2] and is now the standard form.
In mathematics[]
- Forty is a composite number, an octagonal number,[3] and as the sum of the first four pentagonal numbers: 1+5+12+22=40, it is a pentagonal pyramidal number.[4] Adding up some subsets of its divisors (e.g., 1, 4, 5, 10 and 20) gives 40, hence 40 is a semiperfect number.[5]
- Given 40, the Mertens function returns 0.[6] 40 is the smallest number n with exactly 9 solutions to the equation φ(x) = n.
- Forty is the number of n-queens problem solutions for n = 7.
- 40 is a repdigit in base 3 (1111, i.e., 30 + 31 + 32 + 33, or in other words (34 - 1)/2) and a Harshad number in base 10.[7]
In science[]
- The atomic number of zirconium.
- Negative forty is the unique temperature at which the Fahrenheit and Celsius scales correspond; that is, −40 °F = −40 °C. It is referred to as either "minus forty" or "forty below".
Astronomy[]
- Messier object M40, a magnitude 9.0 double star in the constellation Ursa Major
- The New General Catalogue object NGC 40, a magnitude 12.4 planetary nebula in the constellation Cepheus
In religion[]
The number 40 is found in many traditions without any universal explanation for its use. In Jewish, Christian, Islamic, and other Middle Eastern traditions it is taken to represent a large, approximate number, similar to "umpteen".
Sumerian[]
- Enki ( /ˈɛŋki/) or Enkil (Sumerian: dEN.KI(G)