Products of 2-Digit Pairs which Reversed reveal Same Product/Mistake

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Source Work

1986: David Wells: Curious and Interesting Numbers:

The Dictionary
$504$


1997: David Wells: Curious and Interesting Numbers (2nd ed.):

The Dictionary
$504$


Mistake

$504$ is equal to both $12 \times 42$ and $21 \times 24$. There are thirteen such $2$-digit pairs, the largest being $36 \times 84 = 63 \times 48 = 3024$.


There are in fact $14$ such, the largest being $4416 = 46 \times 96 = 64 \times 69$.


Sources