SN7404 inverter strange input low current
Here is what the TI datasheet has to say about the circuit:



It is not possible for this circuit to source less than about 1 mA into a low input.

So what you have cannot be an SN7404. Apparently, you got a recycled chip, and whoever re-applied the label used the wrong one.

To confirm that you have a CMOS chip, measure the output current in both high and low states.