The CAS Registry Mumber 135055-70-8 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, 7 and 0 respectively. Calculate Digit Verification of CAS Registry Number 135055-70: (8*1)+(7*3)+(6*5)+(5*0)+(4*5)+(3*5)+(2*7)+(1*0)=108 108 % 10 = 8 So 135055-70-8 is a valid CAS Registry Number.