The CAS Registry Mumber 71822-39-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,1,8,2 and 2 respectively; the second part has 2 digits, 3 and 9 respectively. Calculate Digit Verification of CAS Registry Number 71822-39: (7*7)+(6*1)+(5*8)+(4*2)+(3*2)+(2*3)+(1*9)=124 124 % 10 = 4 So 71822-39-4 is a valid CAS Registry Number.