137,438,953,471/Historical Note

Historical Note on $137 \, 438 \, 953 \, 471$
$137 \, 438 \, 953 \, 471$ was the $3$rd Mersenne number to be demonstrated composite.

This was done in $1640$ by, who demonstrated it had $223$ as a divisor.

It is in fact the $4$th Mersenne number in sequence to be composite.

However, the status of the $3$rd such composite Mersenne number, $536 \, 870 \, 911$, was not established until 's work in $1732$.