The CAS Registry Mumber 1783-29-5 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,7,8 and 3 respectively; the second part has 2 digits, 2 and 9 respectively. Calculate Digit Verification of CAS Registry Number 1783-29: (6*1)+(5*7)+(4*8)+(3*3)+(2*2)+(1*9)=95 95 % 10 = 5 So 1783-29-5 is a valid CAS Registry Number.