The CAS Registry Mumber 109770-04-9 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,9,7,7 and 0 respectively; the second part has 2 digits, 0 and 4 respectively. Calculate Digit Verification of CAS Registry Number 109770-04: (8*1)+(7*0)+(6*9)+(5*7)+(4*7)+(3*0)+(2*0)+(1*4)=129 129 % 10 = 9 So 109770-04-9 is a valid CAS Registry Number.