The CAS Registry Mumber 127868-57-9 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,7,8,6 and 8 respectively; the second part has 2 digits, 5 and 7 respectively. Calculate Digit Verification of CAS Registry Number 127868-57: (8*1)+(7*2)+(6*7)+(5*8)+(4*6)+(3*8)+(2*5)+(1*7)=169 169 % 10 = 9 So 127868-57-9 is a valid CAS Registry Number.