The CAS Registry Mumber 90417-80-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,0,4,1 and 7 respectively; the second part has 2 digits, 8 and 0 respectively. Calculate Digit Verification of CAS Registry Number 90417-80: (7*9)+(6*0)+(5*4)+(4*1)+(3*7)+(2*8)+(1*0)=124 124 % 10 = 4 So 90417-80-4 is a valid CAS Registry Number.