The CAS Registry Mumber 117835-38-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,7,8,3 and 5 respectively; the second part has 2 digits, 3 and 8 respectively. Calculate Digit Verification of CAS Registry Number 117835-38: (8*1)+(7*1)+(6*7)+(5*8)+(4*3)+(3*5)+(2*3)+(1*8)=138 138 % 10 = 8 So 117835-38-8 is a valid CAS Registry Number.