Issues while looking through values, starting with 0

Hi everyone.
I'm facing the following issue while using elastic 7.6.0.
I have a text field:
"type": "text",
"analyzer": "whitespace"
which contains a values similar to: 06666.
The problem is, when I'm trying to search with (06666) or (fieldName: 06666).
At the very same time I'm getting a correct result after adding either double quotes or wildcard character around the value.

Could someone please elaborate on why this is happening?

Welcome!

Could you provide a full recreation script as described in About the Elasticsearch category. It will help to better understand what you are doing. Please, try to keep the example as simple as possible.

A full reproduction script is something anyone can copy and paste in Kibana dev console, click on the run button to reproduce your use case. It will help readers to understand, reproduce and if needed fix your problem. It will also most likely help to get a faster answer.