The CAS Registry Mumber 16825-27-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,6,8,2 and 5 respectively; the second part has 2 digits, 2 and 7 respectively. Calculate Digit Verification of CAS Registry Number 16825-27: (7*1)+(6*6)+(5*8)+(4*2)+(3*5)+(2*2)+(1*7)=117 117 % 10 = 7 So 16825-27-7 is a valid CAS Registry Number.