The CAS Registry Mumber 383177-83-1 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 3 respectively. Calculate Digit Verification of CAS Registry Number 383177-83: (8*3)+(7*8)+(6*3)+(5*1)+(4*7)+(3*7)+(2*8)+(1*3)=171 171 % 10 = 1 So 383177-83-1 is a valid CAS Registry Number.