Floats field types have their perils. It is the field type that often defaults on an import from Excel, where the field type has to be guessed.
If you try to change the field type to VarChar you get something like “4.00309e+006”
You can first convert from float to bigint and then to VarChar, or create a new VarChar field and use the following SQL. This is for SQL Server.
update tblMyTable set VarCharField = cast(CONVERT(bigint, floatField) as varchar(10))