900

Number
$900$ (nine hundred) is:
 * $2^2 \times 3^2 \times 5^2$


 * The $11$th square number after $1$, $4$, $36$, $121$, $144$, $256$, $324$, $400$, $576$, $784$ to be the $\sigma$ (sigma) value of some (strictly) positive integer:
 * $900 = \map \sigma {472}$


 * The $30$th square number after $1$, $4$, $9$, $16$, $25$, $36$, $\ldots$, $625$, $676$, $729$, $784$, $841$:
 * $900 = 30 \times 30$