The CAS Registry Mumber 68257-98-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,8,2,5 and 7 respectively; the second part has 2 digits, 9 and 8 respectively. Calculate Digit Verification of CAS Registry Number 68257-98: (7*6)+(6*8)+(5*2)+(4*5)+(3*7)+(2*9)+(1*8)=167 167 % 10 = 7 So 68257-98-7 is a valid CAS Registry Number.