diff --git a/baukit/runningstats.py b/baukit/runningstats.py
index 478609f..f37bad5 100644
--- a/baukit/runningstats.py
+++ b/baukit/runningstats.py
@@ -220,7 +220,7 @@ class Stat:
             setattr(self, attr, data_shape)
         else:
             assert x.shape[1:] == data_shape
-        return x.view(x.shape[0], int(numpy.prod(data_shape)))
+        return x.view(x.shape[0], x.shape[1:].numel())
 
     def _restore_result_shape(self, x, attr="data_shape"):
         """
@@ -1185,7 +1185,7 @@ class TopK:
         if self.top_data is None:
             # Allocation: allocate a buffer of size 5*k, at least 10, for each.
             self.data_shape = data.shape[1:]
-            feature_size = int(numpy.prod(self.data_shape))
+            feature_size = self.data_shape.numel()
             self.top_data = torch.zeros(
                 feature_size, max(10, self.k * 5), out=data.new()
             )
@@ -1208,7 +1208,7 @@ class TopK:
         # Pick: copy the top sk of the next batch into the buffer.
         # Currently strided topk is slow.  So we clone after transpose.
         # TODO: remove the clone() if it becomes faster.
-        cdata = data.reshape(size, numpy.prod(data.shape[1:])).t().clone()
+        cdata = data.reshape(size, data.shape[1:].numel()).t().clone()
         td, ti = cdata.topk(sk, sorted=False, largest=self.largest)
         self.top_data[:, self.next : self.next + sk] = td
         if index is not None: