Error in creating the ticket.

Error in creating the ticket.

import requests
import json

auth_token = "#####"
org_id = "####"
ticket_data = {
    "subject": "Testing",
    "contactId": "2575624000007985016",
    "departmentId": "741236985"

headers = {
    "Authorization": auth_token,
    "orgId": org_id,

request ='', headers=headers, data=json.dumps(ticket_data))
if request.status_code == 200:
    print("Request Successful,Response:")
    print("Request not successful,Response code ", request.status_code, " \nResponse : ", request.content)

I have entered the all the feilds like authtoken,orgid,contactid correctly.
I have tried to create a Ticket but it was showing the below error.
Request not successful,Response code  422
Response :  b'{"errorCode":"INVALID_DATA","message":"The data is invalid due to validation restrictions","errors":[{"fieldName":"/contactId","errorType":"invalid","errorMessage":""}]}'

I don't understand what the error is.
Could you please check this and get back to me ASAP.
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