SQL Server 2012 :: How To Convert Varchar Value To INT

I am new to T-SQL development and here's what I am trying to do.

declare @cmd varchar(255)
set @cmd = 'select dbid from sys.sysdatabases where dbid not in (1,2,3,4)'

while (@cmd <=13)
begin
insert into #dbcheck values (@cmd)
Set @cmd = @cmd + 1
end

but it is giving me an error

'Msg 245, Level 16, State 1, Line 3
Conversion failed when converting the varchar value 'select dbid from sys.sysdatabases where dbid not in (1,2,3,4)' to data type int.'

Note - #dbcheck has only one column id int