40 (number)

From Academic Kids

40 is the natural number following 39 and preceding 41. In English, forty is the only number whose constituent letters appear in alphabetical order.

List of numbersIntegers

<< 40 41 42 43 44 45 46 47 48 49 >>

Cardinal forty
Ordinal40th (fortieth)
Numeral system
Factorization<math>2^3 \cdot 5<math>
Divisors 2, 4, 5, 8, 10, 20
Roman numeralXL
Binary101000
Hexadecimal28
Hebrewמ (Mem)

In mathematics

Forty is an octagonal number, and as the sum of the first four pentagonal numbers, it is a pentagonal pyramidal number. It is a Harshad number.

Given 40, the Mertens function returns 0. 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.

In astronomy

In other fields

Forty is also:

es:Cuarenta eo:Kvardek fr:40 (nombre) ko:40 ia:40 it:Quaranta nl:40 (getal) ja:40 pt:Quarenta sl:40 (število) sv:40 (tal) zh:40

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