The CAS Registry Mumber 116885-55-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,6,8,8 and 5 respectively; the second part has 2 digits, 5 and 5 respectively. Calculate Digit Verification of CAS Registry Number 116885-55: (8*1)+(7*1)+(6*6)+(5*8)+(4*8)+(3*5)+(2*5)+(1*5)=153 153 % 10 = 3 So 116885-55-3 is a valid CAS Registry Number.