280 (number)
280 (two hundred [and] eighty) is the natural number after 279 and before 281.
| ||||
---|---|---|---|---|
[[{{#expr: (floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}} (number)|{{#switch:{{{1}}}|-1={{#ifexpr:(floor({{{number}}} div 10)) = 0|-1|←}}|10=→|#default={{#expr:(floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}}}}]] [[{{#expr: (floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}} (number)|{{#switch:{{{1}}}|-1={{#ifexpr:(floor({{{number}}} div 10)) = 0|-1|←}}|10=→|#default={{#expr:(floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}}}}]] [[{{#expr: (floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}} (number)|{{#switch:{{{1}}}|-1={{#ifexpr:(floor({{{number}}} div 10)) = 0|-1|←}}|10=→|#default={{#expr:(floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}}}}]] [[{{#expr: (floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}} (number)|{{#switch:{{{1}}}|-1={{#ifexpr:(floor({{{number}}} div 10)) = 0|-1|←}}|10=→|#default={{#expr:(floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}}}}]] [[{{#expr: (floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}} (number)|{{#switch:{{{1}}}|-1={{#ifexpr:(floor({{{number}}} div 10)) = 0|-1|←}}|10=→|#default={{#expr:(floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}}}}]] [[{{#expr: (floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}} (number)|{{#switch:{{{1}}}|-1={{#ifexpr:(floor({{{number}}} div 10)) = 0|-1|←}}|10=→|#default={{#expr:(floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}}}}]] [[{{#expr: (floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}} (number)|{{#switch:{{{1}}}|-1={{#ifexpr:(floor({{{number}}} div 10)) = 0|-1|←}}|10=→|#default={{#expr:(floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}}}}]] [[{{#expr: (floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}} (number)|{{#switch:{{{1}}}|-1={{#ifexpr:(floor({{{number}}} div 10)) = 0|-1|←}}|10=→|#default={{#expr:(floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}}}}]] [[{{#expr: (floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}} (number)|{{#switch:{{{1}}}|-1={{#ifexpr:(floor({{{number}}} div 10)) = 0|-1|←}}|10=→|#default={{#expr:(floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}}}}]] [[{{#expr: (floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}} (number)|{{#switch:{{{1}}}|-1={{#ifexpr:(floor({{{number}}} div 10)) = 0|-1|←}}|10=→|#default={{#expr:(floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}}}}]] [[{{#expr: (floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}} (number)|{{#switch:{{{1}}}|-1={{#ifexpr:(floor({{{number}}} div 10)) = 0|-1|←}}|10=→|#default={{#expr:(floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}}}}]] [[{{#expr: (floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}} (number)|{{#switch:{{{1}}}|-1={{#ifexpr:(floor({{{number}}} div 10)) = 0|-1|←}}|10=→|#default={{#expr:(floor({{{number}}} div {{{factor}}})) * {{{factor}}}+({{{1}}}*{{{factor}}} div 10)}}}}]] | ||||
Cardinal | two hundred eighty | |||
Ordinal | 280th (two hundred eightieth) | |||
Factorization | 23 × 5 × 7 | |||
Greek numeral | ΣΠ´ | |||
Roman numeral | CCLXXX | |||
Binary | 1000110002 | |||
Ternary | 1011013 | |||
Octal | 4308 | |||
Duodecimal | 1B412 | |||
Hexadecimal | 11816 |
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).
280 is a base 10 Harshad number.
Integers from 281 to 289
281
282
282 = 2·3·47, sphenic number
283
283 prime, twin prime with 281, strictly non-palindromic number
284
285
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
286 = 2·11·13, sphenic number, tetrahedral number, nontotient, also shorthand for the Intel 80286 microprocessor chip.
286 is the smallest even pseudoprime (not divisible by 3) to base 3, which implies 3285 ≡ 1 (mod 286).
287
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
289
289 = 172, centered octagonal number, Friedman number since (8 + 9)2 = 289.
References
- "Sloane's A002805 : Denominators of harmonic numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-28.
- "Sloane's A000567 : Octagonal numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-28.