The CAS Registry Mumber 76782-16-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,6,7,8 and 2 respectively; the second part has 2 digits, 1 and 6 respectively. Calculate Digit Verification of CAS Registry Number 76782-16: (7*7)+(6*6)+(5*7)+(4*8)+(3*2)+(2*1)+(1*6)=166 166 % 10 = 6 So 76782-16-6 is a valid CAS Registry Number.