The CAS Registry Mumber 135182-56-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,5,1,8 and 2 respectively; the second part has 2 digits, 5 and 6 respectively. Calculate Digit Verification of CAS Registry Number 135182-56: (8*1)+(7*3)+(6*5)+(5*1)+(4*8)+(3*2)+(2*5)+(1*6)=118 118 % 10 = 8 So 135182-56-8 is a valid CAS Registry Number.