291

Number
$291$ (two hundred and ninety-one) is:


 * $3 \times 97$


 * The $43$rd happy number after $1$, $7$, $10$, $13$, $19$, $23$, $\ldots$, $188$, $190$, $192$, $193$, $203$, $208$, $219$, $226$, $230$, $236$, $239$, $262$, $263$, $280$:
 * $291 \to 2^2 + 9^2 + 1^2 = 4 + 81 + 1 = 86 \to 8^2 + 6^2 = 64 + 36 = 100 \to 1^2 + 0^2 + 0^2 = 1$