The CAS Registry Mumber 2725-69-1 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 2,7,2 and 5 respectively; the second part has 2 digits, 6 and 9 respectively. Calculate Digit Verification of CAS Registry Number 2725-69: (6*2)+(5*7)+(4*2)+(3*5)+(2*6)+(1*9)=91 91 % 10 = 1 So 2725-69-1 is a valid CAS Registry Number.