The CAS Registry Mumber 90504-39-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,0,5,0 and 4 respectively; the second part has 2 digits, 3 and 9 respectively. Calculate Digit Verification of CAS Registry Number 90504-39: (7*9)+(6*0)+(5*5)+(4*0)+(3*4)+(2*3)+(1*9)=115 115 % 10 = 5 So 90504-39-5 is a valid CAS Registry Number.