Get Parent records Count if Child records are null

 

Single line SOQL: 

SELECT Count(Id) from ParentObject__c where Id Not IN (select Parent(Lookup) field API name from ChildObject__c) and Status_c='Pending' and Recordtype.name ='Normal'

Reference link:

https://salesforce.stackexchange.com/questions/230524/soql-query-to-display-number-of-opportunities-number-of-contacts-from-account