The CAS Registry Mumber 1020718-23-3 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,0,2,0,7,1 and 8 respectively; the second part has 2 digits, 2 and 3 respectively. Calculate Digit Verification of CAS Registry Number 1020718-23: (9*1)+(8*0)+(7*2)+(6*0)+(5*7)+(4*1)+(3*8)+(2*2)+(1*3)=93 93 % 10 = 3 So 1020718-23-3 is a valid CAS Registry Number.