The CAS Registry Mumber 271261-78-0 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 2,7,1,2,6 and 1 respectively; the second part has 2 digits, 7 and 8 respectively. Calculate Digit Verification of CAS Registry Number 271261-78: (8*2)+(7*7)+(6*1)+(5*2)+(4*6)+(3*1)+(2*7)+(1*8)=130 130 % 10 = 0 So 271261-78-0 is a valid CAS Registry Number.