The CAS Registry Mumber 11021-88-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,1,0,2 and 1 respectively; the second part has 2 digits, 8 and 8 respectively. Calculate Digit Verification of CAS Registry Number 11021-88: (7*1)+(6*1)+(5*0)+(4*2)+(3*1)+(2*8)+(1*8)=48 48 % 10 = 8 So 11021-88-8 is a valid CAS Registry Number.