A memory device comprises a plurality of memory cells each having a threshold voltage corresponding to any one of a plurality of program states according to target data to be stored by performing a program operation, page buffers configured to store data provided from a memory controller, a data conversion controller configured to control the page buffers to convert the data into the target data including a plurality of logical page bits and a program operation controller configured to perform the program operation to store the target data in the plurality of memory cells, wherein the plurality of logical page bits include at least one logical page bit distinguishing even program states from odd program states among the plurality of program states and remaining logical page bits other than the at least one logical page bit having a same value as at least one program state among adjacent program states.