There is a function for casting to integer and decimal, but none for casting to a long.
This makes it hard to create a datetime from milliseconds (as a string). If I try to cast directly using datetime("1564694683395"), seems like the string gets truncated to int max value and becomes Fri, Jan 16 1970 @ 12:29:47 AM PST.
The current workaround is to first cast the string to a decimal and store it in a long variable. Then cast the long variable to a date time.