Multiperfect numbers probably need no introduction. (These numbers are defined in Wikipedia and MathWorld.)
I need the answer to the following question as additional context for a research article that I am currently writing:
Who discovered (in the year $1643$) the largest known $3$-perfect number to date?
Here are the six known $3$-perfect numbers, with the last being discovered more than $360$ years ago, in $1643$: \begin{align*} 120 &= 2^3 \times 3 \times 5, \\ 672 &= 2^5 \times 3 \times 7, \\ 523776 &= 2^9 \times 3 \times 11 \times 31, \\ 459818240 &= 2^8 \times 5 \times 7 \times 19 \times 37 \times 73, \\ 1476304896 &= 2^{13} \times 3 \times 11 \times 43 \times 127, \\ 51001180160 &= 2^{14} \times 5 \times 7 \times 19 \times 31 \times 151. \\ \end{align*}
Note that $N$ is an odd perfect number if and only if $2N$ is a (necessarily) even $3$-perfect number. (My profuse thanks to Professor V. M. Misyakov for pointing out my mistake in ResearchGate.)
This link asserts that it was René Descartes who discovered the following multiperfect numbers: \begin{array}{|c|c|c|c|c|} \hline \text{index} & \text{smallest} & \text{name} & \text{ found by } \\ \hline 4 & 30240 & 4-\text{perfect} & \text{Descartes (1638)} \\ \hline 5 & 14182439040 & 5-\text{perfect} & \text{Descartes (1638)} \\ \hline \end{array}
Perhaps \begin{align*} 51001180160 &= 2^{14} \times 5 \times 7 \times 19 \times 31 \times 151 \end{align*} was also discovered by Descartes in $1643$, judging from the timing. Did he?
Dickson's History of the Theory of Numbers - Vol. I (page 36) states that the largest known $3$-perfect number to date ($51001180160 = 2^{14} \times 5 \times 7 \times 19 \times 31 \times 151$) was discovered by Fermat in the year $1643$.
Thank you to Semiclassical for pointing this out in a comment.