The CAS Registry Mumber 25861-45-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,5,8,6 and 1 respectively; the second part has 2 digits, 4 and 5 respectively. Calculate Digit Verification of CAS Registry Number 25861-45: (7*2)+(6*5)+(5*8)+(4*6)+(3*1)+(2*4)+(1*5)=124 124 % 10 = 4 So 25861-45-4 is a valid CAS Registry Number.