The CAS Registry Mumber 107618-17-7 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 8 respectively; the second part has 2 digits, 1 and 7 respectively. Calculate Digit Verification of CAS Registry Number 107618-17: (8*1)+(7*0)+(6*7)+(5*6)+(4*1)+(3*8)+(2*1)+(1*7)=117 117 % 10 = 7 So 107618-17-7 is a valid CAS Registry Number.