The CAS Registry Mumber 1261365-63-2 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,2,6,1,3,6 and 5 respectively; the second part has 2 digits, 6 and 3 respectively. Calculate Digit Verification of CAS Registry Number 1261365-63: (9*1)+(8*2)+(7*6)+(6*1)+(5*3)+(4*6)+(3*5)+(2*6)+(1*3)=142 142 % 10 = 2 So 1261365-63-2 is a valid CAS Registry Number.