The CAS Registry Mumber 101686-03-7 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 6 respectively; the second part has 2 digits, 0 and 3 respectively. Calculate Digit Verification of CAS Registry Number 101686-03: (8*1)+(7*0)+(6*1)+(5*6)+(4*8)+(3*6)+(2*0)+(1*3)=97 97 % 10 = 7 So 101686-03-7 is a valid CAS Registry Number.