The CAS Registry Mumber 2130-30-5 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 2,1,3 and 0 respectively; the second part has 2 digits, 3 and 0 respectively. Calculate Digit Verification of CAS Registry Number 2130-30: (6*2)+(5*1)+(4*3)+(3*0)+(2*3)+(1*0)=35 35 % 10 = 5 So 2130-30-5 is a valid CAS Registry Number.