An interesting passage from The Poison King: The Life and Legend of Mithradates, Rome’s Deadliest Enemy (see this post):
Mithradates’ dazzling memory and facility with languages were legendary in his own time…. Only one other individual in antiquity had linguistic abilities that even approached those of Mithradates. According to Plutarch, Queen Cleopatra of Egypt “spoke many languages and gave audiences to most foreign ambassadors without the help of interpreters.” Aulus Gellius remarked that “he was thoroughly conversant in the dialects of the 25 nations that he ruled, and spoke each language as if it were his native tongue.” …
Which languages did Mithradates speak or read with ease? These are certain: Greek, Macedonian, Persian, Latin, Aramaic/Hebrew, Parthian, Armenian, Old and New Phrygian, Cappadocian, and the Gaulish dialect of his Galatian lover Adobogiona. Other languages may have included Avestan (Old Iranian, used in Zoroastrian prayers); Sanskrit (Hindu medical texts); Egyptian and Punic; Celtic/Gallic (perhaps Allobrogesean, the language of his bodyguard Bituitus). He knew some Anatolian tongues, such as Carian, Mysian, Isaurian, Lydian, Lycian (and Pisidian), and maybe had a smattering of Syriac, Elamite, and Sumerian (used in religious texts of the Seleucid era). He could have learned Italian dialects, Marsic, Oscan, and Umbrian; Thracian (spoken by many of his cavalry regiments; and Getic (spoken in Tomis on the Danube). Other possibilities include vestig[i]al forms of Assyrian or Hittite and dialects of Colchis, Sarmatia, and Scythia.
There are obviously heaping dollops of speculation in that passage (one somehow doubts the Sumerian), but it’s a useful rundown of the linguistic situation in that part of the world a couple of millennia ago. (One wonders, though: why the parentheses around “and Pisidian”?)