The CAS Registry Mumber 11121-57-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,1,1,2 and 1 respectively; the second part has 2 digits, 5 and 7 respectively. Calculate Digit Verification of CAS Registry Number 11121-57: (7*1)+(6*1)+(5*1)+(4*2)+(3*1)+(2*5)+(1*7)=46 46 % 10 = 6 So 11121-57-6 is a valid CAS Registry Number.