The CAS Registry Mumber 76081-17-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,6,0,8 and 1 respectively; the second part has 2 digits, 1 and 7 respectively. Calculate Digit Verification of CAS Registry Number 76081-17: (7*7)+(6*6)+(5*0)+(4*8)+(3*1)+(2*1)+(1*7)=129 129 % 10 = 9 So 76081-17-9 is a valid CAS Registry Number.