240 (number)

From Wikipedia, the free encyclopedia

240 (two hundred [and] forty) is the natural number following 239 and preceding 241.

← 200 210 220 230 240 250 260 270 280 290 → List of numbers — Integers ← 100 110 120 130 140 150 160 170 180 190 →
Cardinal	two hundred [and] forty
Ordinal	two hundred [and] fortieth
Factorization	$240 = 2^4 \cdot 3 \cdot 5$
Roman numeral	CCXL
Binary	11110000
Hexadecimal	F0

[edit] In mathematics

With 20 divisors total (1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 16, 20, 24, 30, 40, 48, 60, 80, 120, and 240) more than any previous number, 240 is a highly composite number, and it is also a refactorable number or tau number, since with 20 divisors and 20 divides 240. And since it has 31 totient answers, more than any previous integer, 240 is a highly totient number.

240 is a semiperfect number.

240 can be expressed as a sum of consecutive primes in two different ways: 240 = 53 + 59 + 61 + 67 = 17 + 19 + 23 + 29 + 31 + 37 + 41 + 43. It can also be expressed as the product of two consecutive integers, 15 and 16, thus 240 is a pronic number.

Also, being divisible by the sum of its digits, 240 is a Harshad number, and not only that, it is also a concatenation of two of its proper divisors (see Sloane's A50480).

E₈ has 240 roots.

[edit] In other fields

240 is:

A common voltage in England and Australia before conversion to 230V standard.
In British currency, the number of pence in a pound until 1971.
A cholesterol level of 240 and above is considered high risk.
The model number of the Convair 240.
The year A.D. 240 or 240 BC.
Nissan 240SX
Volvo 240

[edit] Other numbers from 241 to 249

241 (two hundred forty-one) has its own article.

242 (two hundred forty-two) has its own article.

Two hundred forty-three 243 = 3⁵, perfect totient number, sum of five consecutive primes (41 + 43 + 47 + 53 + 59), Harshad number

Two hundred forty-four 244 = 2²·61, nontotient, noncototient, self number

Two hundred forty-five 245 = 5·7². In the MARC format for records in online public access (library) catalogs, in which each type of information about a book (or other library material) is identified with a 3-digit number, 245 identifies the title of the item; most library catalog software requires that each record have at least a 245 tag, even if no other information is entered about the item.

Two hundred forty-six 246 = 2·3·41, sphenic number, nontotient, untouchable number

Two hundred forty-seven 247 = 13·19, pentagonal number

Sometime (when it is an URL, etc.) may use "247" as an alternate to 24/7, it is an abbreviation which stands for "24 hours a day, 7 days a week".

Two hundred forty-eight 248 = 2³·31, nontotient, untouchable number, refactorable number; E₈ has complex dimension 248.

Two hundred forty-nine 249 = 3·83