Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On a curious property of Bell numbers   In this paper we derive congruences expressing Bell numbers and derangement
numbers in terms of each other modulo any prime.

3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
14
The categories of this paper are: math-ph
7
The categories of this paper are: hep-th
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
23
The categories of this paper are: solv-int
10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex
13
The categories of this paper are: quant-ph
11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an
33
The categories of this paper are: plasm-ph
5
The categories of this paper are: gr-qc