Largest Product of Pandigital Factors

Theorem

The largest integer that can be obtained by multiplying $2$ integers which between them use all the digits from $1$ to $9$ is:

$843 \, 973 \, 902 = 9642 \times 87531$

Proof

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Sources

• 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $9642$
• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $9642$