The CAS Registry Mumber 122651-65-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,2,6,5 and 1 respectively; the second part has 2 digits, 6 and 5 respectively. Calculate Digit Verification of CAS Registry Number 122651-65: (8*1)+(7*2)+(6*2)+(5*6)+(4*5)+(3*1)+(2*6)+(1*5)=104 104 % 10 = 4 So 122651-65-4 is a valid CAS Registry Number.