The CAS Registry Mumber 683775-74-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 6,8,3,7,7 and 5 respectively; the second part has 2 digits, 7 and 4 respectively. Calculate Digit Verification of CAS Registry Number 683775-74: (8*6)+(7*8)+(6*3)+(5*7)+(4*7)+(3*5)+(2*7)+(1*4)=218 218 % 10 = 8 So 683775-74-8 is a valid CAS Registry Number.