The CAS Registry Mumber 75697-51-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,5,6,9 and 7 respectively; the second part has 2 digits, 5 and 1 respectively. Calculate Digit Verification of CAS Registry Number 75697-51: (7*7)+(6*5)+(5*6)+(4*9)+(3*7)+(2*5)+(1*1)=177 177 % 10 = 7 So 75697-51-7 is a valid CAS Registry Number.