The CAS Registry Mumber 1780-94-5 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 0 respectively; the second part has 2 digits, 9 and 4 respectively. Calculate Digit Verification of CAS Registry Number 1780-94: (6*1)+(5*7)+(4*8)+(3*0)+(2*9)+(1*4)=95 95 % 10 = 5 So 1780-94-5 is a valid CAS Registry Number.