2500

Number
$2500$ (two thousand, five hundred) is:


 * $2^2 \times 5^4$


 * The $50$th square number after $1, 4, 9, 16, 25, 36, \ldots, 1521, 1600, 1681, 1764, 1936, 2025, 2116, 2209, 2304, 2401$:
 * $2500 = 50 \times 50$


 * The $43$rd positive integer which cannot be expressed as the sum of a square and a prime:
 * $1$, $10$, $25$, $34$, $58$, $64$, $85$, $\ldots$, $1024$, $1089$, $1225$, $1255$, $1351$, $1414$, $1444$, $1521$, $1681$, $1849$, $1906$, $1936$, $2116$, $2209$, $2304$, $2500$, $\ldots$