Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_21020 ( "Model number" text, "sSpec number" text, "Frequency" text, "GPU frequency" text, "L2 cache" text, "I/O bus" text, "Memory" text, "Voltage" text, "TDP" text, "Socket" text, "Release date" text, "Part number(s)" text, "Release price ( USD )" text )

### Question ###
Name the memory for meodel number for atom e640t

### Accurate SQL ###

SELECT "Memory" FROM table_21020 WHERE "Model number" = 'Atom E640T'