The CAS Registry Mumber 635731-95-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 6,3,5,7,3 and 1 respectively; the second part has 2 digits, 9 and 5 respectively. Calculate Digit Verification of CAS Registry Number 635731-95: (8*6)+(7*3)+(6*5)+(5*7)+(4*3)+(3*1)+(2*9)+(1*5)=172 172 % 10 = 2 So 635731-95-2 is a valid CAS Registry Number.