The CAS Registry Mumber 6206-78-6 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 6,2,0 and 6 respectively; the second part has 2 digits, 7 and 8 respectively. Calculate Digit Verification of CAS Registry Number 6206-78: (6*6)+(5*2)+(4*0)+(3*6)+(2*7)+(1*8)=86 86 % 10 = 6 So 6206-78-6 is a valid CAS Registry Number.