The CAS Registry Mumber 910908-09-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 9,1,0,9,0 and 8 respectively; the second part has 2 digits, 0 and 9 respectively. Calculate Digit Verification of CAS Registry Number 910908-09: (8*9)+(7*1)+(6*0)+(5*9)+(4*0)+(3*8)+(2*0)+(1*9)=157 157 % 10 = 7 So 910908-09-7 is a valid CAS Registry Number.