The CAS Registry Mumber 73185-75-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,3,1,8 and 5 respectively; the second part has 2 digits, 7 and 5 respectively. Calculate Digit Verification of CAS Registry Number 73185-75: (7*7)+(6*3)+(5*1)+(4*8)+(3*5)+(2*7)+(1*5)=138 138 % 10 = 8 So 73185-75-8 is a valid CAS Registry Number.