Python error TypeError: 1535922562 is not serializable JSON

I'm running a script that returns error, but I can not interpret what it refers to.

SELECT * FROM  tabla WHERE id = 'b827eb9eea3e' AND time BETWEEN 1535922562 AND 1535922562
1535922562 index -3 timezone
1535922562 <type 'numpy.int64'> (6, 34)
aqui
1535922562 aqui
Traceback (most recent call last):
  File "process.py", line 166, in <module>
    json.dump(last_processed,f)
  File "/usr/lib/python2.7/json/__init__.py", line 189, in dump
    for chunk in iterable:
  File "/usr/lib/python2.7/json/encoder.py", line 442, in _iterencode
    o = _default(o)
  File "/usr/lib/python2.7/json/encoder.py", line 184, in default
    raise TypeError(repr(o) + " is not JSON serializable")
TypeError: 1535922562 is not JSON serializable