+640 represents a [Number](/wiki/Number) with specific mathematical properties. As the year [640 AD](/wiki/640_AD), it marks a pivotal moment in [Early History](/wiki/Early_History), witnessing significant shifts in power and culture across continents.
+## See also
+- [Chronology](/wiki/Chronology)
+- [Mathematics](/wiki/Mathematics)
+- [Ancient World](/wiki/Ancient_World)
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