158

Number

$158$ (one hundred and fifty-eight) is:

$2 \times 79$

One of the factors of one of the terms of one of the $2$ representations of $635 \, 318 \, 657$ as the sum of $2$ fourth powers:

$635 \, 318 \, 657 = 59^4 + 158^4$

The $22$nd nontotient:

$\nexists m \in \Z_{>0}: \map \phi m = 158$

where $\map \phi m$ denotes the Euler $\phi$ function