What is the biggest software development team that uses Python? I am wondering how well the dynamic type system scales to large development teams.
It's pretty clear that at Google they have C++ and Java codebases with thousands of developers; their use of Python is much smaller.
Are there some huge companies that develop primarily in Python?
Our project is over 30,000 lines of Python.  That's probably small by some standards.  But it's plenty big enough to fill my little brain.  The application is mentioned in our annual report, so it's "strategic" in that sense.  We're not a "huge" company, so we don't really qualify.
A "huge company" (Fortune 1000?) doesn't develop primarily in any single language.  Large companies will have lots of development teams, each using a different technology, depending on -- well -- on nothing in particular.
When you get to "epic companies" (Fortune 10) you're looking at an organization that's very much like a conglomerate of several huge companies rolled together.  Each huge company within an epic company is still a huge company with multiple uncoordinated IT shops doing unrelated things -- there's no "develop primarily in" any particular language or toolset.
Even for "large companies" and "small companies" (like ours) you still have fragmentation.  Our in-house IT is mostly Microsoft.  Our other product development is mostly Java.  My team, however, doesn't have much useful specification, so we use Python.  We use python because of the duck typing and dynamic programming features.
(I don't know what a dynamic type system is -- Python types are static -- when you create an object, its type can never change.)
Since no huge company develops primarily in any particular language or toolset, the trivial answer to your question is "No" for any language or tool.  And No for Python in particular.
Biggest python projects