The CAS Registry Mumber 121154-53-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,1,1,5 and 4 respectively; the second part has 2 digits, 5 and 3 respectively. Calculate Digit Verification of CAS Registry Number 121154-53: (8*1)+(7*2)+(6*1)+(5*1)+(4*5)+(3*4)+(2*5)+(1*3)=78 78 % 10 = 8 So 121154-53-8 is a valid CAS Registry Number.