The CAS Registry Mumber 155213-41-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,5,5,2,1 and 3 respectively; the second part has 2 digits, 4 and 1 respectively. Calculate Digit Verification of CAS Registry Number 155213-41: (8*1)+(7*5)+(6*5)+(5*2)+(4*1)+(3*3)+(2*4)+(1*1)=105 105 % 10 = 5 So 155213-41-5 is a valid CAS Registry Number.