Using SSIS to import the Excel spreadsheet - you would use a conditional split transformation to redirect rows from the source to separate destinations.
In the conditional split - you would define each output rule, something like:
SUBSTRING(AccountNumber, 1, 1) = 1
SUBSTRING(AccountNumber, 1, 1) <> 1
In each destination you define which table is used to receive the data.
With that said - working with Excel and SSIS can be problematic because SSIS is a x86 (32-bit) application and if you are using the x64 version of Office you cannot load the Excel driver. If you can export the Excel spreadsheet to a CSV file that is much easier to use in SSIS.
Another option would be to not worry about splitting the data to other tables in the process to upload the data to SQL Server. Upload the data to a staging table - then use T-SQL to insert the data into the appropriate final tables. That would be fairly simple code:
INSERT INTO dbo.AccountsStartingWith1
SELECT * FROM stage.InputTable WHERE AccountNumber Like '1%';
INSERT INTO dbo.AccountsNotStartingWith1
SELECT * FROM stage.InputTable WHERE AccountNumber Not Like '1%';