The CAS Registry Mumber 287398-41-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 2,8,7,3,9 and 8 respectively; the second part has 2 digits, 4 and 1 respectively. Calculate Digit Verification of CAS Registry Number 287398-41: (8*2)+(7*8)+(6*7)+(5*3)+(4*9)+(3*8)+(2*4)+(1*1)=198 198 % 10 = 8 So 287398-41-8 is a valid CAS Registry Number.