The CAS Registry Mumber 214355-25-6 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 2,1,4,3,5 and 5 respectively; the second part has 2 digits, 2 and 5 respectively. Calculate Digit Verification of CAS Registry Number 214355-25: (8*2)+(7*1)+(6*4)+(5*3)+(4*5)+(3*5)+(2*2)+(1*5)=106 106 % 10 = 6 So 214355-25-6 is a valid CAS Registry Number.