One thing that seems to distinguish parables from accounts of actual events is the absence of specific names for the people in the parables. In the parables we read, "A sower" (Luke 8), "A rich man" (Luke 12, 15), "A man" (Luke 13, 14), "A Samaritan" (Luke 10).
However, in the account of the Rich Man and the Beggar, we are actually given the name of the beggar. This is quite a distinction from all the other parables. In addition, Jesus tells us that the rich man saw another specific man--the patriarch Abraham.
So, the fact that the rich man's name is withheld does support the idea of this being a parable. Yet, the fact that two other specific people are identified by name seems to be stronger evidence to support the idea that this was an actual historical event with actual people.
The significance of this story comes in the reference to someone rising from the dead, as Jesus states that even if someone rises from the dead, some will not believe. This is fulfilled in the fact that Jesus rose from the dead, and even the chief priests of the day continued in their refusal to believe in Him.
19 “There was a rich man who was clothed in purple and fine linen and
who feasted sumptuously every day. 20 And at his gate was laid a poor
man named Lazarus, covered with sores, 21 who desired to be fed with
what fell from the rich man's table. Moreover, even the dogs came and
licked his sores. 22 The poor man died and was carried by the angels
to Abraham's side.The rich man also died and was buried, 23 and in
Hades, being in torment, he lifted up his eyes and saw Abraham far off
and Lazarus at his side. 24 And he called out, ‘Father Abraham, have
mercy on me, and send Lazarus to dip the end of his finger in water
and cool my tongue, for I am in anguish in this flame.’ 25 But Abraham
said, ‘Child, remember that you in your lifetime received your good
things, and Lazarus in like manner bad things; but now he is comforted
here, and you are in anguish. 26 And besides all this, between us and
you a great chasm has been fixed, in order that those who would pass
from here to you may not be able, and none may cross from there to
us.’ 27 And he said, ‘Then I beg you, father, to send him to my
father's house— 28 for I have five brothers—so that he may warn them,
lest they also come into this place of torment.’ 29 But Abraham said,
‘They have Moses and the Prophets; let them hear them.’ 30 And he
said, ‘No, father Abraham, but if someone goes to them from the dead,
they will repent.’ 31 He said to him, ‘If they do not hear Moses and
the Prophets, neither will they be convinced if someone should rise
from the dead.’” Luke 16:19-31 ESV