R - I am looking for a function to Extract the last n digits from a Text variable and Save them in a New variable For thousand of Cases

Question

I am looking for a function through which i can extract the last N digits from a Variable and save them in a New Variable in the same dataset. The dataset which i have is in the data.table format. I have around thousand of variables in my data frame so listing the data for some of them:

CaseID Var1 Var2 Var3

298710 1 1 2

399761 3 1 1

200987 1 5 3

Now, the function which i am looking for is something in which i can enter the number of digits to extract from CaseID variable and it will create a new variable as shown below:

CaseID Var1 Var2 Var3 Newvar

298710 1 1 2 0

399761 3 1 1 1

200987 1 5 3 7

Please note in my data, the class of CaseID is of Character type.

if you could help me out here then it would be really helpful.

Thanks in advance.