The CAS Registry Mumber 193953-57-0 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,9,3,9,5 and 3 respectively; the second part has 2 digits, 5 and 7 respectively. Calculate Digit Verification of CAS Registry Number 193953-57: (8*1)+(7*9)+(6*3)+(5*9)+(4*5)+(3*3)+(2*5)+(1*7)=180 180 % 10 = 0 So 193953-57-0 is a valid CAS Registry Number.