The CAS Registry Mumber 63283-55-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,3,2,8 and 3 respectively; the second part has 2 digits, 5 and 5 respectively. Calculate Digit Verification of CAS Registry Number 63283-55: (7*6)+(6*3)+(5*2)+(4*8)+(3*3)+(2*5)+(1*5)=126 126 % 10 = 6 So 63283-55-6 is a valid CAS Registry Number.