The CAS Registry Mumber 97813-50-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,7,8,1 and 3 respectively; the second part has 2 digits, 5 and 0 respectively. Calculate Digit Verification of CAS Registry Number 97813-50: (7*9)+(6*7)+(5*8)+(4*1)+(3*3)+(2*5)+(1*0)=168 168 % 10 = 8 So 97813-50-8 is a valid CAS Registry Number.