The CAS Registry Mumber 107613-71-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,7,6,1 and 3 respectively; the second part has 2 digits, 7 and 1 respectively. Calculate Digit Verification of CAS Registry Number 107613-71: (8*1)+(7*0)+(6*7)+(5*6)+(4*1)+(3*3)+(2*7)+(1*1)=108 108 % 10 = 8 So 107613-71-8 is a valid CAS Registry Number.