1600

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


 * $2^6 \times 5^2$


 * The $15$th square number after $1$, $4$, $36$, $121$, $144$, $256$, $324$, $400$, $576$, $784$, $900$, $961$, $1024$, $1296$ to be the $\sigma$ (sigma) value of some (strictly) positive integer:
 * $1600 = \map \sigma {\cdots}$


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