The CAS Registry Mumber 1217447-55-6 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,2,1,7,4,4 and 7 respectively; the second part has 2 digits, 5 and 5 respectively. Calculate Digit Verification of CAS Registry Number 1217447-55: (9*1)+(8*2)+(7*1)+(6*7)+(5*4)+(4*4)+(3*7)+(2*5)+(1*5)=146 146 % 10 = 6 So 1217447-55-6 is a valid CAS Registry Number.