The CAS Registry Mumber 122203-78-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,2,2,0 and 3 respectively; the second part has 2 digits, 7 and 8 respectively. Calculate Digit Verification of CAS Registry Number 122203-78: (8*1)+(7*2)+(6*2)+(5*2)+(4*0)+(3*3)+(2*7)+(1*8)=75 75 % 10 = 5 So 122203-78-5 is a valid CAS Registry Number.