The CAS Registry Mumber 100008-86-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,0,0,0 and 8 respectively; the second part has 2 digits, 8 and 6 respectively. Calculate Digit Verification of CAS Registry Number 100008-86: (8*1)+(7*0)+(6*0)+(5*0)+(4*0)+(3*8)+(2*8)+(1*6)=54 54 % 10 = 4 So 100008-86-4 is a valid CAS Registry Number.