2001: multiplicity(x, x) == 1

This function seeks the largest m such that p**m divides n.
It should exit quickly with int 1 when p and n are the same.
Test added.

sympy/ntheory/factor_.py

@@ -47,6 +47,8 @@ def multiplicity(p, n):
 
     """
 
+    if p == n:
+        return 1
     if p == 2:
         return trailing(n)
 

sympy/ntheory/tests/test_ntheory.py

@@ -31,6 +31,8 @@ def test_multiplicity():
             assert multiplicity(b, (b**i) * 1000249) == i
     # Should be fast
     assert multiplicity(10, 10**10023) == 10023
+    # Should exit quick
+    assert multiplicity(1, 1) == 1
 
 def test_perfect_power():
     assert perfect_power(0) == None