It is a TMP431-5BP IC with a Toshiba label on it. 40 pin DIL. My guesses are:
CPU
ROM chip where all of the games/main "program" is stored
Datasheet sites return nothing
4-BIT 1 CHIP MICROCOMPUTER / 64x4 RAM / 1536x8 ROM
My advice would be, don't mess with it. Its probably doing the job that would be done with a PIC or AVR these days.
Theres probably an EPROM nearby that stores the actual data or OS for whatever it is.
It is a vtech lesson one