The CAS Registry Mumber 6517-30-2 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 6,5,1 and 7 respectively; the second part has 2 digits, 3 and 0 respectively. Calculate Digit Verification of CAS Registry Number 6517-30: (6*6)+(5*5)+(4*1)+(3*7)+(2*3)+(1*0)=92 92 % 10 = 2 So 6517-30-2 is a valid CAS Registry Number.