Add unit tests and whatsnew info

Author: Aliebc

doc/source/whatsnew/v3.0.0.rst

@@ -749,6 +749,7 @@ I/O
 - Bug in :meth:`read_stata` where the missing code for double was not recognised for format versions 105 and prior (:issue:`58149`)
 - Bug in :meth:`set_option` where setting the pandas option ``display.html.use_mathjax`` to ``False`` has no effect (:issue:`59884`)
 - Bug in :meth:`to_excel` where :class:`MultiIndex` columns would be merged to a single row when ``merge_cells=False`` is passed (:issue:`60274`)
+- Bug in :meth:`to_json` raising ``OverflowError`` when convert DataFrame.dtypes Series to JSON (:issue:`61170`)
 
 Period
 ^^^^^^

pandas/_libs/src/vendored/ujson/python/ujson.c

@@ -212,8 +212,8 @@ int object_is_na_type(PyObject *obj) {
   return result;
 }
 
-int object_is_ndtypes_type(PyObject * obj){
-  PyObject * ndtype = (PyObject*)&PyArrayDescr_Type;
+int object_is_ndtypes_type(PyObject *obj) {
+  PyObject *ndtype = (PyObject *)&PyArrayDescr_Type;
   int result = PyObject_IsInstance(obj, ndtype);
   if (result == -1) {
     PyErr_Clear();

pandas/tests/io/json/test_pandas.py

@@ -2311,3 +2311,19 @@ def test_large_number():
     )
     expected = Series([9999999999999999])
     tm.assert_series_equal(result, expected)
+
+
+@pytest.mark.parametrize(
+    "dataframe, expected_json",
+    [
+        (DataFrame({"A": [1, 2, 3], "B": [4, 5, 6]}), '{"A":"int64","B":"int64"}'),
+        (
+            DataFrame({"X": [1.1, 2.2], "Y": ["a", "b"]}),
+            '{"X":"float64","Y":"object"}',
+        ),
+    ],
+)
+def test_dtypes_to_json(dataframe: DataFrame, expected_json):
+    # GH 61170
+    dtypes_json = dataframe.dtypes.to_json()
+    assert json.loads(dtypes_json) == json.loads(expected_json)