The CAS Registry Mumber 4525-71-7 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,5,2 and 5 respectively; the second part has 2 digits, 7 and 1 respectively. Calculate Digit Verification of CAS Registry Number 4525-71: (6*4)+(5*5)+(4*2)+(3*5)+(2*7)+(1*1)=87 87 % 10 = 7 So 4525-71-7 is a valid CAS Registry Number.