The CAS Registry Mumber 86911-87-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,6,9,1 and 1 respectively; the second part has 2 digits, 8 and 7 respectively. Calculate Digit Verification of CAS Registry Number 86911-87: (7*8)+(6*6)+(5*9)+(4*1)+(3*1)+(2*8)+(1*7)=167 167 % 10 = 7 So 86911-87-7 is a valid CAS Registry Number.