The CAS Registry Mumber 6306-86-1 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 6,3,0 and 6 respectively; the second part has 2 digits, 8 and 6 respectively. Calculate Digit Verification of CAS Registry Number 6306-86: (6*6)+(5*3)+(4*0)+(3*6)+(2*8)+(1*6)=91 91 % 10 = 1 So 6306-86-1 is a valid CAS Registry Number.