The CAS Registry Mumber 105798-30-9 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,5,7,9 and 8 respectively; the second part has 2 digits, 3 and 0 respectively. Calculate Digit Verification of CAS Registry Number 105798-30: (8*1)+(7*0)+(6*5)+(5*7)+(4*9)+(3*8)+(2*3)+(1*0)=139 139 % 10 = 9 So 105798-30-9 is a valid CAS Registry Number.