The CAS Registry Mumber 6247-13-8 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 6,2,4 and 7 respectively; the second part has 2 digits, 1 and 3 respectively. Calculate Digit Verification of CAS Registry Number 6247-13: (6*6)+(5*2)+(4*4)+(3*7)+(2*1)+(1*3)=88 88 % 10 = 8 So 6247-13-8 is a valid CAS Registry Number.