The CAS Registry Mumber 101685-98-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,1,6,8 and 5 respectively; the second part has 2 digits, 9 and 8 respectively. Calculate Digit Verification of CAS Registry Number 101685-98: (8*1)+(7*0)+(6*1)+(5*6)+(4*8)+(3*5)+(2*9)+(1*8)=117 117 % 10 = 7 So 101685-98-7 is a valid CAS Registry Number.