1638

Number
$1638$ (one thousand, six hundred and thirty-eight) is:


 * $2 \times 3^2 \times 7 \times 13$


 * The $8$th Ore number after $1$, $6$, $28$, $140$, $270$, $496$, $672$:
 * $\dfrac {1638 \times \map \tau {1638} } {\map \sigma {1638} } = 9$
 * and the $6$th after $1$, $6$, $14$, $270$, $672$ whose divisors also have an arithmetic mean which is an integer:
 * $\dfrac {\map \sigma {1638} } {\map \tau {1638} } = 84$