The CAS Registry Mumber 109645-25-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,9,6,4 and 5 respectively; the second part has 2 digits, 2 and 5 respectively. Calculate Digit Verification of CAS Registry Number 109645-25: (8*1)+(7*0)+(6*9)+(5*6)+(4*4)+(3*5)+(2*2)+(1*5)=132 132 % 10 = 2 So 109645-25-2 is a valid CAS Registry Number.