The CAS Registry Mumber 262601-81-0 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 2,6,2,6,0 and 1 respectively; the second part has 2 digits, 8 and 1 respectively. Calculate Digit Verification of CAS Registry Number 262601-81: (8*2)+(7*6)+(6*2)+(5*6)+(4*0)+(3*1)+(2*8)+(1*1)=120 120 % 10 = 0 So 262601-81-0 is a valid CAS Registry Number.