Question: How many books were said to be written by the most influential in Islamic philosophy?

Knowledge 1: History of science
Ibn Sina (Avicenna) is regarded as the most influential philosopher of Islam. He pioneered the science of experimental medicine and was the first physician to conduct clinical trials. His two most notable works in medicine are the Kitāb al-shifāʾ ("Book of Healing") and The Canon of Medicine, both of which were used as standard medicinal texts in both the Muslim world and in Europe well into the 17th century. Amongst his many contributions are the discovery of the contagious nature of infectious diseases, and the introduction of clinical pharmacology. [SEP] Knowledge 2: Muslim world
One of the common definitions for "Islamic philosophy" is "the style of philosophy produced within the framework of Islamic culture." Islamic philosophy, in this definition is neither necessarily concerned with religious issues, nor is exclusively produced by Muslims. The Persian scholar Ibn Sina (Avicenna) (980–1037) had more than 450 books attributed to him. His writings were concerned with various subjects, most notably philosophy and medicine. His medical textbook The Canon of Medicine was used as the standard text in European universities for centuries. He also wrote The Book of Healing, an influential scientific and philosophical encyclopedia.
Knowledge 1: History of science
Ibn Sina (Avicenna) is regarded as the most influential philosopher of Islam. He pioneered the science of experimental medicine and was the first physician to conduct clinical trials. His two most notable works in medicine are the Kitāb al-shifāʾ ("Book of Healing") and The Canon of Medicine, both of which were used as standard medicinal texts in both the Muslim world and in Europe well into the 17th century. Amongst his many contributions are the discovery of the contagious nature of infectious diseases, and the introduction of clinical pharmacology. [SEP] Knowledge 2: Political philosophy
Islamic political philosophy, was, indeed, rooted in the very sources of Islam—i.e., the Qur'an and the Sunnah, the words and practices of Muhammad—thus making it essentially theocratic. However, in the Western thought, it is generally supposed that it was a specific area peculiar merely to the great philosophers of Islam: al-Kindi (Alkindus), al-Farabi (Abunaser), İbn Sina (Avicenna), Ibn Bajjah (Avempace), Ibn Rushd (Averroes), and Ibn Khaldun. The political conceptions of Islam such as kudrah (power), sultan, ummah, cemaa (obligation)-and even the "core" terms of the Qur'an—i.e., ibadah (worship), din (religion), rab (master) and ilah (deity)—is taken as the basis of an analysis. Hence, not only the ideas of the Muslim political philosophers but also many other jurists and ulama posed political ideas and theories. For example, the ideas of the Khawarij in the very early years of Islamic history on Khilafa and Ummah, or that of Shia Islam on the concept of Imamah are considered proofs of political thought. The clashes between the Ehl-i Sunna and Shia in the 7th and 8th centuries had a genuine political character.
Knowledge 1: History of science
Ibn Sina (Avicenna) is regarded as the most influential philosopher of Islam. He pioneered the science of experimental medicine and was the first physician to conduct clinical trials. His two most notable works in medicine are the Kitāb al-shifāʾ ("Book of Healing") and The Canon of Medicine, both of which were used as standard medicinal texts in both the Muslim world and in Europe well into the 17th century. Amongst his many contributions are the discovery of the contagious nature of infectious diseases, and the introduction of clinical pharmacology. [SEP] Knowledge 2: Avicenna
Avicenna was a devout Muslim and sought to reconcile rational philosophy with Islamic theology. His aim was to prove the existence of God and His creation of the world scientifically and through reason and logic. Avicenna's views on Islamic theology (and philosophy) were enormously influential, forming part of the core of the curriculum at Islamic religious schools until the 19th century. Avicenna wrote a number of short treatises dealing with Islamic theology. These included treatises on the prophets (whom he viewed as "inspired philosophers"), and also on various scientific and philosophical interpretations of the Quran, such as how Quranic cosmology corresponds to his own philosophical system. In general these treatises linked his philosophical writings to Islamic religious ideas; for example, the body's afterlife.

Answer: 450