206

Number
$206$ (two hundred and six) is:


 * $2 \times 103$


 * The $30$th nontotient:
 * $\nexists m \in \Z_{>0}: \phi \left({m}\right) = 206$
 * where $\phi \left({m}\right)$ denotes the Euler $\phi$ function


 * The $19$th noncototient after $10, 26, 34, 50, 52, 58, 86, 100, 116, 122, 130, 134, 146, 154, 170, 172, 186, 202$:
 * $\nexists m \in \Z_{>0}: m - \phi \left({m}\right) = 206$
 * where $\phi \left({m}\right)$ denotes the Euler $\phi$ function


 * The $11$th untouchable number after $2, 5, 52, 88, 96, 120, 124, 146, 162, 188$.


 * The $2$nd positive integer solution after $14$ to $\sigma \left({n}\right) = \sigma \left({n + 1}\right)$:
 * $\sigma \left({206}\right) = 312 = \sigma \left({207}\right)$


 * The $5$th positive integer after $200, 202, 204, 205$ that cannot be made into a prime number by changing just $1$ digit