PLAYABLE AT 720p NORMAL SETTINGS.
The i5 7400 is highly enough.
But, what about the GPU, which is the main in deciding gaming? I expect you do not have as separate GPU as you haven't mentioned it, so given that you rely on on-board graphics, YOU CAN PLAY IT! At an okay-ish 720p Normal settings, 24 frames/second.
RAM of 4GB is a pain given that some of RAM as used Video RAM (if you do not have a separate graphics card), the system will lag a bit, just don't multitask and play GTA 5, close apps before playing.
If you have a card, 4GB RAM would not be that big of an issue.
I play it at 30fps, on GT 710(which is worse than on-board on yours) and i3-4350T, 4GB RAM.