255

Number
$255$ (two hundred and fifty-five) is:
 * $3 \times 5 \times 17$


 * The $7$th positive integer solution after $1, 3, 15, 104, 164, 194$ to $\phi \left({n}\right) = \phi \left({n + 1}\right)$:
 * $\phi \left({255}\right) = 128 = \phi \left({256}\right)$