How many Prophets are there? and how many of them are Arabs ?

Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Allah Says in the Qur'an (Interpretation of meaning): (Mankind were one community and Allâh sent Prophets with glad tidings and warnings, and with them He sent the Scripture in truth to judge between people in matters wherein they differed. And only those to whom (the Scripture) was given differed concerning it after clear proofs had come unto them through hatred, one to another. Then Allâh by His Leave guided those who believed to the truth of that wherein they differed. And Allâh guides whom He wills to a Straight Path). [2:213].
Imam al-Qurtubi mentioned in his explanation of the above verse that the number of the Prophets is a hundred and twenty four thousand and that the Messengers among them are three hundred and thirteen and those mentioned in the Qur'an with their proper names are eighteen.
And Ibn Kathir stated in his explanation that there is disagreement among the scholars over the number of Prophets and Messengers. He stated so when explaining the following verse : (And Messengers We have mentioned to you before, and Messengers We have not mentioned to you, - and to Mûsa (Moses) Allâh spoke directly). [4:164].

But what is narrated from Imam al-Qurtubi and others specifying the number of Prophets is not correct.
As for Abu Dhar's Hadith which states expressly the number of Prophets, most of the scholars believe that it is a weak Hadith. Some scholars even declare that this Hadith is fabricated. In this Hadith it is said that the Arab Prophets are (Hud, Saleh, Shuaib and Muhammad) (Blessings and peace of Allah be upon them all).
Shaikh al-Islam Ibn Taymiyah said that Muslims should believe in all the Prophets as a group and refrain from arguing about their number. This is the right opinion.
Allah knows best.