Is paying zakaat al-fitr obligatory for someone who only prayed on the last day of Ramadan and did not fast?

In the answer to question no.
2182 we stated that the one who
does not pray is a kaafir, whether he does not pray out of carelessness and
laziness or because he denies it is obligatory. 

If Allah guides a person (to Islam) before sunset on the last
day of Ramadan, he has to pay zakaat al-fitr, regardless of whether he
caught up with the fast or not, because of the hadeeth of Ibn ‘Umar (may
Allah be pleased with him) who said: The Messenger of Allah (blessings and
peace of Allah be upon him) enjoined the sadaqah of Ramadan upon the people,
a saa‘ of dates or a saa‘ of barley, upon every person, free or slave, male
or female, among the Muslims.

Narrated by al-Bukhaari, 1503; Muslim, 984. 

The words “among the Muslims” are general in meaning and
include everyone who became Muslim before sunset on the last day of Ramadan,
even if he did not fast. 

Ibn Qudaamah (may Allah have mercy on him) said: … With
regard to the time when it becomes obligatory, it is when the Sun sets on
the last day of Ramadan. It becomes obligatory with the setting of the sun
on the last day of the month of Ramadan, so whoever becomes Muslim before
sunset has to pay zakaat al-fitr, but if he became Muslim after sunset, he
is not obliged to pay it. … al-Layth, Abu Thawr and ashaab al-ra’y said: It
becomes obligatory when dawn breaks on the day of Eid, and this was also
narrated from Maalik, because it is an act of worship that has to do with
Eid, so it does not become obligatory before the day of Eid.

End quote from al-Mughni, 2/358 

Al-Nawawi (may Allah have mercy on him) said: The correct
view in our opinion is that it becomes obligatory when the sun sets on the
night before Eid al-Fitr. This was the view of al-Thawri, Ahmad and Ishaaq,
and is mentioned in one report from Maalik. Abu Haneefah and his companions,
Abu Thawr, Dawood and another reported that Maalik said that it becomes
obligatory when dawn breaks.

End quote from al-Majmoo‘, 6/88. See also Haashiyat
al-‘Adawi, 1/515 

If he became Muslim after sunset on the last day of Ramadan,
then he does not have to pay zakaat al-fitr, because the month has ended,
except in the opinion of those who say that it becomes obligatory when dawn
breaks. The more correct view is that of the majority of scholars, because
of the words of Ibn ‘Umar (may Allah be pleased with him): The Messenger of
Allah (blessings and peace of Allah be upon him) enjoined zakaat al-fitr
after Ramadan. Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said: The
end of the fast of Ramadan comes when the sun sets on the night before Eid
al-Fitr.

End quote from al-Sharh al-Mumti‘, 6/56.