Big number modolo a small integer in Openssl

Question

Hi everyone, I was wondering if it is possible that a big number modolo a samll integer in Openssl? Say I generate 2 big prime numbers:

BN_generate_prime(p,512,0,0,0,0,0);
BN_generate_prime(q,512,0,0,0,0,0);

and calculate the product N:

BN_mul(N,p,q,ctx);

I would like to test if N is a "Blum iteger" (N mod 4==3), however I can't figure out how to do this since function BN_mod only support big numbers.

Thanks!