The CAS Registry Mumber 90520-79-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,0,5,2 and 0 respectively; the second part has 2 digits, 7 and 9 respectively. Calculate Digit Verification of CAS Registry Number 90520-79: (7*9)+(6*0)+(5*5)+(4*2)+(3*0)+(2*7)+(1*9)=119 119 % 10 = 9 So 90520-79-9 is a valid CAS Registry Number.