Upper limit of data type Number (Integer) is 2,147,483,647. I've

Have you tried to use Number(Decimal) it should go as high as 2^53 -1. If that is still not enough you have to store it as text. But then you might not be able to do any calculations in Appian without using special plugins.

Thanks for the inputs

if the data type is changed in CDT, what will happen to the existing processes ?

reason I'm asking is, when ever we add objects to CDT we face issues with deployments to higher environments. we have to manually delete the CDT and then import the XSD again .. so, will the existing processes continue to run on the older version (or) new version of CDT ?

Running instances are generally not affected and keep running with the old version of the CDT. Problems arise as soon you call sub processes with the CDT as parameter and have the "By reference" checkbox set.

It might be necessary to modify some models to be able to handle both data types. Be shure to test all cases.

Similar question if there is any solution / workaround is available :

------------
In our case, we have CDT which accepts Number data type (It can be integer/decimal) - so we have used floating point field which will allow decimals along with integer. Now when we add more than 7 digits, the value rounds off. While using integer fields which comes with a validation of total max length 2,147,483,647 ,it is converted to exponential.

We can't use text as Number is defined data type of CDT, and also we want to allow decimals, is there any way we can achieve this using floating point field?

Example:
Value used is 123456789
After entering, it's automatically rounded up to be 123456800
In Tempo, it shows 1.234568e 08