The CAS Registry Mumber 1505-68-6 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,5,0 and 5 respectively; the second part has 2 digits, 6 and 8 respectively. Calculate Digit Verification of CAS Registry Number 1505-68: (6*1)+(5*5)+(4*0)+(3*5)+(2*6)+(1*8)=66 66 % 10 = 6 So 1505-68-6 is a valid CAS Registry Number.