240 (number)
Encyclopedia : 2 : 24 : 240 : 240 (number)
240 (two hundred [and] forty) is the natural number following 239 and preceding 241.
| |
| Cardinal | two [and] hundred forty |
| Ordinal | two [and] hundred fortieth |
| Factorization | [240 = 2^4 \cdot 3 \cdot 5] |
| Roman numeral | CCXL |
| Binary | 11110000 |
| Hexadecimal | F0 |
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).
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.
Other numbers from 241 to 249
Two hundred forty-one 241 regular prime, twin prime with 239 and a lucky prime.
Two hundred forty-two 242 = 2·112, nontotient, totient sum for first 28 integers
Two hundred forty-three 243 = 35, 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
Two hundred forty-eight 248 = 23·31, nontotient, untouchable number, refactorable number, also area code for telephone calls in Oakland County and part of Macomb County in Michigan
Two hundred forty-nine 249 = 3·83
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