diff --git a/README.rst b/README.rst
index aa5a8290..10ea7ee9 100755
--- a/README.rst
+++ b/README.rst
@@ -127,6 +127,11 @@ There you'll find a list of all the methods, types and available constructors.
 
 More examples are also available under the ``telethon_examples/`` folder.
 
+If you're using Telethon under ARM, you may want to install ``sympy`` through
+``pip`` for a substantial speed-up when generating the keys required to
+connect to Telegram (you can of course do this on desktop too). See
+`issue #199 <https://github.com/LonamiWebs/Telethon/issues/199>`_ for more.
+
 Common errors
 -------------
 
diff --git a/telethon/crypto/factorization.py b/telethon/crypto/factorization.py
index e6601f5a..12a03af3 100644
--- a/telethon/crypto/factorization.py
+++ b/telethon/crypto/factorization.py
@@ -1,4 +1,8 @@
 from random import randint
+try:
+    import sympy.ntheory
+except ImportError:
+    sympy = None
 
 
 class Factorization:
@@ -58,5 +62,8 @@ class Factorization:
     @staticmethod
     def factorize(pq):
         """Factorizes the given number and returns both the divisor and the number divided by the divisor"""
-        divisor = Factorization.find_small_multiplier_lopatin(pq)
-        return divisor, pq // divisor
+        if sympy:
+            return tuple(sympy.ntheory.factorint(pq).keys())
+        else:
+            divisor = Factorization.find_small_multiplier_lopatin(pq)
+            return divisor, pq // divisor