Laws of the Megillah
9. The most desirable way to fulfill the mitzvah ("Mitzvah Min HaMuvchar")
is to hear the reading of the Megillah in a synagogue, where there are many
people (as implied by proverbs 12:28,) "Within the multitude of the people
is the glory of the King." At the very least, one should hear the Megillah
in "Minyan" of ten [adult men].
If it is impossible to [hear it] being read in a "Minyan," each individual
should read the Megillah himself from a kosher scroll, reciting the
blessings beforehand. If there is one person who knows how to read it, and
the others do not, the person who knows should read the Megillah and the
others should listen and [will] fulfill their obligation, even though ten
[adult men] are not in attendance.
The blessing after [the reading of the Megillah] is recited only when ten
[adult males] are present. However, even an individual may recite the
blessing after the reading, if he omits G-d's Name and mention of His
Kingship (that is, "Elokeinu Melech HaOlam").