The CAS Registry Mumber 810-83-3 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 8,1 and 0 respectively; the second part has 2 digits, 8 and 3 respectively. Calculate Digit Verification of CAS Registry Number 810-83: (5*8)+(4*1)+(3*0)+(2*8)+(1*3)=63 63 % 10 = 3 So 810-83-3 is a valid CAS Registry Number.