19,600

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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

Also see

• Previous  ... Next: Tetrahedral Number
• Previous  ... Next: Square Number

• Previous: Square and Tetrahedral Numbers

Sources

• 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $19,600$
• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $19,600$