10.19 PrevPrimeInt

PrevPrimeInt( n )

PrevPrimeInt returns the largest prime which is strictly smaller than the integer n.

Note that PrevPrimeInt uses a probable-primality test (see IsPrimeInt).

    gap> PrevPrimeInt( 541 );
    523
    gap> PrevPrimeInt( 1 );
    -2 

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GAP 3.4.4
April 1997