The CAS Registry Mumber 102108-47-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,2,1,0 and 8 respectively; the second part has 2 digits, 4 and 7 respectively. Calculate Digit Verification of CAS Registry Number 102108-47: (8*1)+(7*0)+(6*2)+(5*1)+(4*0)+(3*8)+(2*4)+(1*7)=64 64 % 10 = 4 So 102108-47-4 is a valid CAS Registry Number.