The CAS Registry Mumber 135055-66-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,5,0,5 and 5 respectively; the second part has 2 digits, 6 and 6 respectively. Calculate Digit Verification of CAS Registry Number 135055-66: (8*1)+(7*3)+(6*5)+(5*0)+(4*5)+(3*5)+(2*6)+(1*6)=112 112 % 10 = 2 So 135055-66-2 is a valid CAS Registry Number.