The CAS Registry Mumber 193601-91-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,9,3,6,0 and 1 respectively; the second part has 2 digits, 9 and 1 respectively. Calculate Digit Verification of CAS Registry Number 193601-91: (8*1)+(7*9)+(6*3)+(5*6)+(4*0)+(3*1)+(2*9)+(1*1)=141 141 % 10 = 1 So 193601-91-1 is a valid CAS Registry Number.