The CAS Registry Mumber 66441-50-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,6,4,4 and 1 respectively; the second part has 2 digits, 5 and 0 respectively. Calculate Digit Verification of CAS Registry Number 66441-50: (7*6)+(6*6)+(5*4)+(4*4)+(3*1)+(2*5)+(1*0)=127 127 % 10 = 7 So 66441-50-7 is a valid CAS Registry Number.