2809

Number
$2809$ (two thousand, eight hundred and nine) is:


 * $53^2$


 * The $53$rd square number after $1, 4, 9, 16, 25, 36, \ldots, 1521, 1600, 1681, 1764, 1936, 2025, 2116, 2209, 2304, 2401, 2500, 2601, 2704$:
 * $2809 = 53 \times 53$


 * The $44$th positive integer which cannot be expressed as the sum of a square and a prime:
 * $1$, $10$, $25$, $34$, $58$, $64$, $85$, $\ldots$, $1521$, $1681$, $1849$, $1906$, $1936$, $2116$, $2209$, $2304$, $2500$, $2809$, $\ldots$