19,600

Number
$19 \, 600$ (nineteen thousand, six hundred) is:


 * $2^4 \times 5^2 \times 7^2$


 * The $140$th square number:
 * $19 \, 600 = 140 \times 140$


 * The $48$th tetrahedral number:
 * $19 \, 600 = \ds \sum_{k \mathop = 1}^{48} \frac {k \paren {k + 1} } 2 = \dfrac {48 \paren {48 + 1} \paren {48 + 2} } 6$


 * The $3$rd and last after $1$, $4$ of the $3$ tetrahedral numbers which are also square

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