Hmm... I tried it and I got 
  P&|@*/ mul 

346052331





> From: [email protected]
> To: [email protected]
> Date: Fri, 31 Jul 2015 12:16:20 -0400
> Subject: [Jprogramming] multiplication bug
> 
> i am trying to multiply several integers modulo small prime number here and 
> fail at that.
> 
> ------------------------ 
> 
>    NB. highest power of prime x that divides !y
> 
>    pffact=:([: +/ ] <.@% [ ^ 1 + [: i. <.@^.)
> 
>    P=:9+1e9
> 
>    pw=.1e9 pffact">~ pr=.p:i.240 NB. first few primes and their powers
> 
>    1 p: P NB. P is prime
> 
> 1
>    datatype P
> integer
> 
> ------------------------ 
> here is a list of integers I am trying to multiply
> ------------------------ 
> 
>    mul=.1+pr (P&|@^) 2 (P&|@*) pw
>    datatype mul
> integer
> 
> ------------------------ 
> And here is what happens when I actually multiply them:
> ------------------------ 
> 
>       P&|@*/ mul
> 0
> 
> ------------------------
> which is not the right answer
> ------------------------ 
> 
>       P&|@*/ |.mul
> 3.90562e7
> 
> ------------------------ 
> 
> 
>                                         
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