Hello Meghal,
The maximum number of Scheduled Analytics Rules in Azure Sentinel is 512.
I am unable to search for this in the official documentation, but I know for sure that 512 is the number at this moment (not sure if it will be increased or not in the future).
You can decrease the number of analytics rules you create, by making use of dynamic content of the Alert Details (meaning that the same analytic rule could generate multiple types of alerts - ex. critical or medium severity, based on the properties returned by the Query, allowing you to have just 1 rule for multiple severities, rather than multiple copies of the same rule with different severity configuration for example).
BR,
George