The Prophet Muhammed was not an illiterate
Many lies have been told about our Great Prophet (peace be upon him and his family). One of them is that he was an illiterate. This was the claim uttered by his evil wife, Aisha, in which she stated that the Prophet confessed his inability to read whilst he was approached by Gabriel during his first revelation. 
Let alone that this lie degrades our Prophet (peace be upon him and his family) and has made millions of non-Muslims belittle his value and character, it is sufficient to know that Aisha’s story is but a fabrication for the fact that she was not present during the same events she is narrating, in addition to that she narrates the event in a direct transmission and not through another narrator who would be closer to the event than herself.
Imam al-Jawad's refutation of Aisha's lie
Our Imam Mohammad al-Jawad (peace be upon him) had a great role in refuting the lies of the likes of Aisha, and he stressed the falsity of these tales, to the extent that he asked Almighty God (Exalted is He) to deprive of His Mercy whoever claims that the Prophet (peace be upon him and his family) was illiterate. For instance, it is reported that a companion of Imam al-Jawad, whose name was Ali, son of Asbat, said:
«I said to Abu Jafar (i.e. Imam al-Jawad): The people are claiming that the Prophet (may God’s blessings be upon him and his family) could neither write nor read. Upon then, he (peace be upon him) denied it and said: They have lied! May God curse them! How can such a thing be, when God (Exalted is He) said: (It is) He who sent amongst the Ummis (i.e. from ‘Umm-ul Qura’, another name for Mecca) a Messenger amongst them who recites for them His Signs and purifies them and teaches them the Book and Wisdom, even though before him they were on clear deviation.  How can he teach them the Book and Wisdom, and yet not know how to read and write?»
Upon then, Ali, son of Asbat, asked: «Then why was he called ‘the Ummi Prophet’?» The Imam replied: «Because he was ascribed to Mecca. That is the Word of God (Exalted is He): That you may warn Umm-ul-Qura (Mecca) and those surrounding it.  Thus, he was named an Ummi for that reason.» 
The Prophet had multilingual abilities
In another report narrated by a companion named Jafar, son of Mohammad as-Sufi, with a similar formulation, Imam Mohammad al-Jawad (peace be upon him) similarly condemned those who utter such lies about the Prophet (peace be upon him and his family). Additionally, he states that the Prophet was able to read and write in more than seventy languages:
«By God, indeed, the Messenger of God (may God’s blessings be upon him and his family) used to read and write in seventy two - or he said - seventy-three languages. He was only named an ‘Ummi’ because he was from the people of Mecca, and Mecca is Umm-ul-Qura (meaning: Mother of Cities).» 
Does the Qur'an state the Prophet's illiteracy?
The group that refers to itself as ‘Ahlus-Sunnah wal-Jama’a’ often argue with the following verse of the Holy Qur’an to assist their false belief in the Prophet’s illiteracy: «And you did not recite before it any book, nor did you inscribe one with your right hand. Otherwise, the falsifiers would have had (a cause for) doubt.» 
However, this verse does in no way state the Prophet’s illiteracy. It rather states that the Prophet (peace be upon him and his family) did not recite (recitation differs from reading) nor practically write a book, which is, of course, different than the ability to read and write.
The reason, however, to why the Prophet refrained from reciting other written works and practically writing a book by himself, was to repel any eventual accusations from his enemies who claimed that the Holy Qur’an is but an altered copy of other written works.
 Sahih Bukhari, Book 1, Hadith #3.
 The Quran 62:3.
 Ibid., 6:93.
 Al-Saffar, Mohammad son of Hassan. Basa’er-ul-Darajat. Beirut: Aalami Est., 2010. P. 263-264.
 Al-Qummi, Mohammad son of Ali son of Hussain son of Babawayh, Ma’ani’l-Akhbar. Beirut: Dar-ul-Marifa, 1979. P. 53-54.
 The Qur'an 29:49.