Canon 5DS R has a 51.0MP Full frame (36 x 24 mm ) sized CMOS sensor and features Dual DIGIC 6 processor. You can shoot at maximum resolution of 8688 x 5792 pixels with aspect ratios of 3:2 and 16:9. 5DS R has a native ISO range of 100 - 6400 which can be boosted to 12800 and it can save files in RAW format which gives you a wider room for post processing.
Canon 5DS R is not the highest resolution Full frame camera. Sony A7R IV with its 61.0MP sensor is leading in this class. Check the comparison of Canon 5DS R vs Sony A7R IV or take a look at Highest resolution DSLR cameras list.
Canon 5DS R DxOMark Sensor Scores
DxOMark is a benchmark that scientifically assesses image quality of camera sensors. Canon 5DS R sensor has been tested by DxO Mark and got an overall score of 86 for its image quality. You can find the details of their analysis of Canon 5DS R here.
Another important feature about Canon 5DS R's sensor is the lack of anti-alias (Low-pass) filter. Removing anti-aliasing filter increases the sharpness and level of detail but on the other side it also increases the chance of moire occurring in certain scenes.
Let's look at how the size of the Canon 5DS R's Full frame sensor compares with other standard sensor sizes.