The CAS Registry Mumber 155919-09-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,5,5,9,1 and 9 respectively; the second part has 2 digits, 0 and 9 respectively. Calculate Digit Verification of CAS Registry Number 155919-09: (8*1)+(7*5)+(6*5)+(5*9)+(4*1)+(3*9)+(2*0)+(1*9)=158 158 % 10 = 8 So 155919-09-8 is a valid CAS Registry Number.