The CAS Registry Mumber 32904-90-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,2,9,0 and 4 respectively; the second part has 2 digits, 9 and 0 respectively. Calculate Digit Verification of CAS Registry Number 32904-90: (7*3)+(6*2)+(5*9)+(4*0)+(3*4)+(2*9)+(1*0)=108 108 % 10 = 8 So 32904-90-8 is a valid CAS Registry Number.