280 (number)
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|---|---|---|---|---|
| Cardinal | two hundred eighty | |||
| Ordinal | 280th (two hundred and eightieth) |
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| Factorization | 23× 5 × 7 | |||
| Roman numeral | CCLXXX | |||
| Binary | 1000110002 | |||
| Ternary | 1011013 | |||
| Quaternary | 101204 | |||
| Quinary | 21105 | |||
| Senary | 11446 | |||
| Octal | 4308 | |||
| Duodecimal | 1B412 | |||
| Hexadecimal | 11816 | |||
| Vigesimal | E020 | |||
| Base 36 | 7S36 | |||
280 (two hundred [and] eighty) is the natural number after 279 and before 281.
Contents
In mathematics
The denominator of the eighth harmonic number,[1] 280 is an octagonal number.[2]
There are 280 plane trees with ten nodes. As a consequence of this, 18 people around a round table can shake hands with each other in non-crossing ways, in 280 different ways (this includes rotations).[disputed ]
280 is a base 10 Harshad number.
In geography
See also the year 280.
281 to 289
281
Two hundred [and] eighty-one 281 prime, twin prime with 283, Sophie Germain prime, sum of the first fourteen primes, sum of seven consecutive primes (29 + 31 + 37 + 41 + 43 + 47 + 53), Chen prime, Eisenstein prime with no imaginary part, centered decagonal number
282
Two hundred [and] eighty-two 282 = 2·3·47, sphenic number
283
Two hundred [and] eighty-three 283 prime, twin prime with 281, strictly non-palindromic number
284
Two hundred [and] eighty-four 284= 2·2·71, amicable number with 220; nontotient. 284 degrees Celsius is the flash point of paper.
285
Two hundred [and] eighty-five 285 = 3·5·19, sphenic number, square pyramidal number, Harshad number, also in Star Trek, the total number of Rules of Acquisition, repdigit in base 7 (555).
286
Two hundred [and] eighty-six 286 = 2·11·13, sphenic number, tetrahedral number, nontotient, also shorthand for the Intel 80286 microprocessor chip
287
Two hundred [and] eighty-seven 287 = 7·41, sum of three consecutive primes (89 + 97 + 101), sum of five consecutive primes (47 + 53 + 59 + 61 + 67), sum of nine consecutive primes (17 + 19 + 23 + 29 + 31 + 37 + 41 + 43 + 47), Kynea number, pentagonal number, also shorthand for the Intel math coprocessor to the 80286
288
Two hundred [and] eighty-eight 288 = 25·32, is a pentagonal pyramidal number, is 4 superfactorial since 288 = 1!·2!·3!·4!, is an untouchable number, a Harshad number in base 10, a self number, is sum of the sequence of integers 1..4 to the second tetration since 288 = 1 + 4 + 27 + 256 = 11 + 22 + 33 + 44, the number of labelled pointed rooted trees (vertebrates) with up to 4 nodes, the number of maximal directed Pseudoforests on up to 4 vertices, the number of Endofunctions for all sets with <=4 points, and is two dozen sets of a dozen, thus being two gross, often told as a pun in maths classes, the average surface temperature of Earth on the Kelvin temperature scale.
289
Two hundred [and] eighty-nine 289 = 172, centered octagonal number, Friedman number since (8 + 9)^2 = 289.
