The CAS Registry Mumber 101354-20-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,1,3,5 and 4 respectively; the second part has 2 digits, 2 and 0 respectively. Calculate Digit Verification of CAS Registry Number 101354-20: (8*1)+(7*0)+(6*1)+(5*3)+(4*5)+(3*4)+(2*2)+(1*0)=65 65 % 10 = 5 So 101354-20-5 is a valid CAS Registry Number.