The CAS Registry Mumber 118355-47-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,8,3,5 and 5 respectively; the second part has 2 digits, 4 and 7 respectively. Calculate Digit Verification of CAS Registry Number 118355-47: (8*1)+(7*1)+(6*8)+(5*3)+(4*5)+(3*5)+(2*4)+(1*7)=128 128 % 10 = 8 So 118355-47-8 is a valid CAS Registry Number.