The CAS Registry Mumber 109838-64-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,9,8,3 and 8 respectively; the second part has 2 digits, 6 and 4 respectively. Calculate Digit Verification of CAS Registry Number 109838-64: (8*1)+(7*0)+(6*9)+(5*8)+(4*3)+(3*8)+(2*6)+(1*4)=154 154 % 10 = 4 So 109838-64-4 is a valid CAS Registry Number.