The CAS Registry Mumber 67831-76-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,7,8,3 and 1 respectively; the second part has 2 digits, 7 and 6 respectively. Calculate Digit Verification of CAS Registry Number 67831-76: (7*6)+(6*7)+(5*8)+(4*3)+(3*1)+(2*7)+(1*6)=159 159 % 10 = 9 So 67831-76-9 is a valid CAS Registry Number.