Korselt's Theorem/Historical Note

Historical Note on Korselt's Theorem

Alwin Reinhold Korselt first demonstrated this result in $1899$, but did not actually identify any integers that fulfilled the criterion.

That did not happen until Robert Daniel Carmichael found that $561$ was such a number in $1910$.

It turns out that Václav Šimerka had already found the first $7$ Carmichael numbers in $1885$, but his work was not noticed at the time.