Factoring with ECM

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Hi, I am trying to find factors less than 2**64 of :

1290612864847963913537949591324251934176100028588482946303315059818300684542385803424464362865291275472094774514980695711187516725164679024089451950519195950869825549270090848786866731004441727282214961891312211392627935805630364654739647738980189658558312079777

I know that one exists : 2327913506176773601. I use ecmfactor with B1=1000000. I get the output (False, None) in 5 out of 7 tries, and (True, 2327913506176773601, 3375616994), (True, 2327913506176773601, 2815703546) in the other 2 tries.

Is there a way I can improve the probablity of getting the factor in the above example? I tried different B1 values, but were not very useful. Any other recommendations or suggestions? Your help is very much appreciated.

Thank you Shyam