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:
 * $1, 10, 25, 34, 58, 64, 85, \ldots, 1521, 1681, 1849, 1906, 1936, 2116, 2209, 2304, 2500, \ldots$