1521

Number
$1521$ (one thousand five hundred and twenty-one) is:


 * $3^2 \times 13^2$


 * The $39$th square number after $1, 4, 9, 16, 25, 36, \ldots, 625, 676, 729, 784, 841, 900, 961, 1024, 1089, 1156, 1225, 1296, 1369, 1444$:
 * $1521 = 39 \times 39$