diff --git a/ChangeLog b/ChangeLog
index 06fd1f8..9e2fc93 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2003-12-02  Richard B. Kreckel  <kreckel@ginac.de>
+
+	* examples/perfnum.cc: update to presumed 40th Mersenne prime.
+
 2003-08-06  Richard Kreckel  <kreckel@ginac.de>
 
 	* src/numtheory/cl_nt_sqrtmodp.cc: #undef _R.
diff --git a/examples/perfnum.cc b/examples/perfnum.cc
index 45f3f3a..a5612a5 100644
--- a/examples/perfnum.cc
+++ b/examples/perfnum.cc
@@ -8,8 +8,8 @@ using namespace cln;
 
 int main ()
 {
-	// previous ones were 1257787, 1398269, 2976221, 3021377, 6972593
-	int p = 13466917;
+	// previous ones were 1257787, 1398269, 2976221, 3021377, 6972593, 13466917
+	int p = 20996011;
 	cl_I x = (((cl_I)1 << p) - 1) << (p-1);
 	cout << x << endl;
 }