771

Number
$730$ (seven hundred and thirty) is:
 * $2 \times 5 \times 73$


 * The $13$th non-square positive integer which cannot be expressed as the sum of a square and a prime:
 * $10$, $34$, $58$, $85$, $91$, $130$, $214$, $226$, $370$, $526$, $706$, $730$, $771$, $\ldots$


 * The $25$th positive integer which cannot be expressed as the sum of a square and a prime:
 * $1$, $10$, $25$, $34$, $58$, $64$, $85$, $91$, $121$, $130$, $169$, $196$, $214$, $226$, $289$, $324$, $370$, $400$, $526$, $529$, $625$, $676$, $706$, $730$, $771$, $\ldots$