The CAS Registry Mumber 4371-04-4 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,3,7 and 1 respectively; the second part has 2 digits, 0 and 4 respectively. Calculate Digit Verification of CAS Registry Number 4371-04: (6*4)+(5*3)+(4*7)+(3*1)+(2*0)+(1*4)=74 74 % 10 = 4 So 4371-04-4 is a valid CAS Registry Number.