The CAS Registry Mumber 201863-65-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 2,0,1,8,6 and 3 respectively; the second part has 2 digits, 6 and 5 respectively. Calculate Digit Verification of CAS Registry Number 201863-65: (8*2)+(7*0)+(6*1)+(5*8)+(4*6)+(3*3)+(2*6)+(1*5)=112 112 % 10 = 2 So 201863-65-2 is a valid CAS Registry Number.