The CAS Registry Mumber 111557-82-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,1,5,5 and 7 respectively; the second part has 2 digits, 8 and 2 respectively. Calculate Digit Verification of CAS Registry Number 111557-82: (8*1)+(7*1)+(6*1)+(5*5)+(4*5)+(3*7)+(2*8)+(1*2)=105 105 % 10 = 5 So 111557-82-5 is a valid CAS Registry Number.