286

Number
$286$ (two hundred and eighty-six) is:


 * $2 \times 11 \times 13$


 * The $11$th tetrahedral number, after $1, 4, 10, 20, 35, 56, 84, 120, 165, 220$:
 * $286 = 1 + 3 + 6 + 10 + 15 + 21 + 28 + 36 + 45 + 55 + 66 = \dfrac {11 \left({11 + 1}\right) \left({11 + 2}\right)} 6$


 * The $11$th heptagonal number after $1, 7, 18, 34, 55, 81, 112, 148, 189, 235$:
 * $286 = 1 + 7 + 11 + 16 + 21 + 26 + 31 + 36 + 41 + 46 + 51 = \dfrac {11 \left({5 \times 11 - 3}\right)} 2$


 * The $3$rd Fermat pseudoprime to base $3$ after $91, 121$:
 * $3^{286} \equiv 3 \pmod {121}$


 * The $46$th nontotient:
 * $\nexists m \in \Z_{>0}: \phi \left({m}\right) = 286$
 * where $\phi \left({m}\right)$ denotes the Euler $\phi$ function


 * The $2$nd of the $3$-digit integers $m$ which need the largest number of reverse-and-add process iterations ($23$) before reaching a palindromic number:
 * $286, 968, 1837, \ldots, 8713200023178$