Definition:Perfect Number/Historical Note

Historical Note on Perfect Number
The first $4$ perfect numbers:
 * $6, 18, 496, 8128$

were known to the ancient Greeks.

All were listed by both and.

made the following conjectures:
 * One Perfect Number for Each Number of Digits
 * Last Digit of Perfect Numbers Alternates between $6$ and $8$

both of which are seen to be incorrect from the next few instances in the sequence:
 * $6, 28, 496, 8128, 33 \, 550 \, 336, 8 \, 589 \, 869 \, 056, \ldots$

A manuscript of $1456$ correctly gives the $5$th perfect number as $33 \, 550 \, 536$.