Took me a moment to realize the reason my first attempt got an arithmetic overflow was because your number is in milliseconds - not seconds, which I
believe is the standard expectation for a unix timestamp.
Naturally, you're gonna need to be sure which you're dealing with for this to work.
{DATEADD(Seconds|1970-01-01 00:00:00Z|u|{MATH(Divide|Double|1687818708818|1000|#0)}|yyyy-MM-dd)}