The CAS Registry Mumber 1619-25-6 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,6,1 and 9 respectively; the second part has 2 digits, 2 and 5 respectively. Calculate Digit Verification of CAS Registry Number 1619-25: (6*1)+(5*6)+(4*1)+(3*9)+(2*2)+(1*5)=76 76 % 10 = 6 So 1619-25-6 is a valid CAS Registry Number.