The CAS Registry Mumber 97090-73-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,7,0,9 and 0 respectively; the second part has 2 digits, 7 and 3 respectively. Calculate Digit Verification of CAS Registry Number 97090-73: (7*9)+(6*7)+(5*0)+(4*9)+(3*0)+(2*7)+(1*3)=158 158 % 10 = 8 So 97090-73-8 is a valid CAS Registry Number.