How do i multiply a large number in sql with out getting a "overflow error " error

I know ths maybe a silly question but how do i multiply large numbers in sql server without getting an " Arithmetic overflow error converting expression to data type int " error ? I need to take a column that contains a list of 6 digit client numbers

Eg 123456, 123457 and make it 1234560000000 , 1234570000000 etc.

This is what i tried doing.

update account set sClientIdNo =  sClientIdNo * 100000000

But i end up with the overflow error. Any help will be greatly appriciated.

Thanks