50

Number
$50$ (fifty) is:
 * $2 \times 5^2$


 * The $4$th noncototient after $10, 26, 34$:
 * $\nexists m \in \Z_{>0}: m - \phi \left({m}\right) = 50$
 * where $\phi \left({m}\right)$ denotes the Euler $\phi$ function