The CAS Registry Mumber 55934-99-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,5,9,3 and 4 respectively; the second part has 2 digits, 9 and 9 respectively. Calculate Digit Verification of CAS Registry Number 55934-99: (7*5)+(6*5)+(5*9)+(4*3)+(3*4)+(2*9)+(1*9)=161 161 % 10 = 1 So 55934-99-1 is a valid CAS Registry Number.