The CAS Registry Mumber 1019617-42-5 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,0,1,9,6,1 and 7 respectively; the second part has 2 digits, 4 and 2 respectively. Calculate Digit Verification of CAS Registry Number 1019617-42: (9*1)+(8*0)+(7*1)+(6*9)+(5*6)+(4*1)+(3*7)+(2*4)+(1*2)=135 135 % 10 = 5 So 1019617-42-5 is a valid CAS Registry Number.