The CAS Registry Mumber 5180-83-6 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 5,1,8 and 0 respectively; the second part has 2 digits, 8 and 3 respectively. Calculate Digit Verification of CAS Registry Number 5180-83: (6*5)+(5*1)+(4*8)+(3*0)+(2*8)+(1*3)=86 86 % 10 = 6 So 5180-83-6 is a valid CAS Registry Number.