The CAS Registry Mumber 71715-82-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,1,7,1 and 5 respectively; the second part has 2 digits, 8 and 2 respectively. Calculate Digit Verification of CAS Registry Number 71715-82: (7*7)+(6*1)+(5*7)+(4*1)+(3*5)+(2*8)+(1*2)=127 127 % 10 = 7 So 71715-82-7 is a valid CAS Registry Number.