The CAS Registry Mumber 1217263-83-6 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,2,1,7,2,6 and 3 respectively; the second part has 2 digits, 8 and 3 respectively. Calculate Digit Verification of CAS Registry Number 1217263-83: (9*1)+(8*2)+(7*1)+(6*7)+(5*2)+(4*6)+(3*3)+(2*8)+(1*3)=136 136 % 10 = 6 So 1217263-83-6 is a valid CAS Registry Number.