The CAS Registry Mumber 383177-86-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 3,8,3,1,7 and 7 respectively; the second part has 2 digits, 8 and 6 respectively. Calculate Digit Verification of CAS Registry Number 383177-86: (8*3)+(7*8)+(6*3)+(5*1)+(4*7)+(3*7)+(2*8)+(1*6)=174 174 % 10 = 4 So 383177-86-4 is a valid CAS Registry Number.