The CAS Registry Mumber 116835-16-6 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,6,8,3 and 5 respectively; the second part has 2 digits, 1 and 6 respectively. Calculate Digit Verification of CAS Registry Number 116835-16: (8*1)+(7*1)+(6*6)+(5*8)+(4*3)+(3*5)+(2*1)+(1*6)=126 126 % 10 = 6 So 116835-16-6 is a valid CAS Registry Number.