The CAS Registry Mumber 82191-10-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,2,1,9 and 1 respectively; the second part has 2 digits, 1 and 0 respectively. Calculate Digit Verification of CAS Registry Number 82191-10: (7*8)+(6*2)+(5*1)+(4*9)+(3*1)+(2*1)+(1*0)=114 114 % 10 = 4 So 82191-10-4 is a valid CAS Registry Number.