50

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


 * The $5$th nontotient after $14, 26, 34, 38$:
 * $\nexists m \in \Z_{>0}: \phi \left({m}\right) = 50$
 * where $\phi \left({m}\right)$ denotes the Euler $\phi$ function


 * 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


 * The $2$nd term of the $1$st $5$-tuple of consecutive integers have the property that they are not values of the $\sigma$ function $\sigma \left({n}\right)$ for any $n$:
 * $\left({49, 50, 51, 52, 53}\right)$