1600

Number
$1600$ (one thousand six hundred) is:


 * $2^6 \times 5^2$


 * The $40$th square number after $1, 4, 9, 16, 25, 36, \ldots, 1024, 1089, 1156, 1225, 1296, 1369, 1444, 1521$:
 * $1600 = 40 \times 40$