The following documentation comment has been logged on the website:
Page: https://www.postgresql.org/docs/13/functions-math.html
Description:
The left argument of the operator square root |/ and cube root ||/ in the
current documentation is double precision. But to my experience that should
also work on any numeric types including smallint, integer, bigint, real and
numeric. I have tested it on both PostgreSQL server 12 and 13.