JavaScript
let s = "6964KBYY54Eo8TZSVdsupHij+BWlI5owUQ2Pw9cqBSyw2pyJV4sS+n6k4n6IFu9wtIM,1606802560116"
window.btoa(s)
"Njk2NEtCWVk1NEVvOFRaU1Zkc3VwSGlqK0JXbEk1b3dVUTJQdzljcUJTeXcycHlKVjRzUytuNms0bjZJRnU5d3RJTSwxNjA2ODAyNTYwMTE2"

Python
import base64
s = "6964KBYY54Eo8TZSVdsupHij+BWlI5owUQ2Pw9cqBSyw2pyJV4sS+n6k4n6IFu9wtIM,1606802560116"
# "Njk2NEtCWVk1NEVvOFRaU1Zkc3VwSGlqK0JXbEk1b3dVUTJQdzljcUJTeXcycHlKVjRzUytuNms0bjZJRnU5d3RJTSwxNjA2ODAyNTYwMTE2"
n = base64.b64encode(s.encode())
print(n.decode())