The CAS Registry Mumber 58816-78-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,8,8,1 and 6 respectively; the second part has 2 digits, 7 and 8 respectively. Calculate Digit Verification of CAS Registry Number 58816-78: (7*5)+(6*8)+(5*8)+(4*1)+(3*6)+(2*7)+(1*8)=167 167 % 10 = 7 So 58816-78-7 is a valid CAS Registry Number.