The CAS Registry Mumber 117600-77-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,7,6,0 and 0 respectively; the second part has 2 digits, 7 and 7 respectively. Calculate Digit Verification of CAS Registry Number 117600-77: (8*1)+(7*1)+(6*7)+(5*6)+(4*0)+(3*0)+(2*7)+(1*7)=108 108 % 10 = 8 So 117600-77-8 is a valid CAS Registry Number.