278 (number)
{{Infobox number
| number = 278
| divisor = 1, 2, 139, 278
}}
278 (two hundred [and] seventy-eight) is the natural number following 277 and preceding 279.
In mathematics
- 278 is an even composite number with 2 prime factors.{{Cite web|url=https://mathworld.wolfram.com/CompositeNumber.html|title=Composite numbers|website=mathworld.wolfram.com}}
- 278 is equal to Φ(30). It is the sum of the totient function.{{cite OEIS|A002088|Sum of totient function: a(n) = Sum_{k=1..n} phi(k)}}
- 278 is a nontotient number which means that it is an even number that doesn't follow Euler's totient function.{{Cite web|url=https://mathworld.wolfram.com/Nontotient.html|website=mathworld.wolfram.com|title=Nontotient numbers}}
- 278 is the smallest semiprime number that has an anagram that is also semiprime. The other number is 287.{{Cite web|url=https://mathworld.wolfram.com/Semiprime.html|title=Semiprime numbers|website=mathworld.wolfram.com}}