The CAS Registry Mumber 1019540-88-5 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,0,1,9,5,4 and 0 respectively; the second part has 2 digits, 8 and 8 respectively. Calculate Digit Verification of CAS Registry Number 1019540-88: (9*1)+(8*0)+(7*1)+(6*9)+(5*5)+(4*4)+(3*0)+(2*8)+(1*8)=135 135 % 10 = 5 So 1019540-88-5 is a valid CAS Registry Number.