The CAS Registry Mumber 63131-17-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,3,1,3 and 1 respectively; the second part has 2 digits, 1 and 7 respectively. Calculate Digit Verification of CAS Registry Number 63131-17: (7*6)+(6*3)+(5*1)+(4*3)+(3*1)+(2*1)+(1*7)=89 89 % 10 = 9 So 63131-17-9 is a valid CAS Registry Number.