The CAS Registry Mumber 1837-05-4 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,8,3 and 7 respectively; the second part has 2 digits, 0 and 5 respectively. Calculate Digit Verification of CAS Registry Number 1837-05: (6*1)+(5*8)+(4*3)+(3*7)+(2*0)+(1*5)=84 84 % 10 = 4 So 1837-05-4 is a valid CAS Registry Number.