EIGRP AS :
Range is : 1-65535
You can configure more than one EIGRP autonomous system on the same router, but Cisco does not recommend it. Multiple EIGRP autonomous systems on the same router that use mutual redistribution can cause discrepancies in the EIGRP topology table. Cisco recommends you configure only one EIGRP autonomous system in any single autonomous system. Also use another protocol, such as BGP, in order to connect the two EIGRP autonomous systems.
AS numbers are globally unique numbers that are used to identify ASes, and which enable an AS to exchange exterior routing information between neighboring ASes. An AS is a connected group of IP networks that adhere to a single and clearly defined routing policy.
BGP :
Range : 1-65535
There are a limited number of available AS numbers. Therefore, it is important to determine which sites require unique AS numbers and which do not. Sites that do not require a unique AS number should use one or more of the AS numbers reserved for private use, which are in the range from 64512 to 65535
As EIGRP is interior routing protocol..there is no harm in using any AS number for Enterprise Network , in EIGRP.
See below link for more information..
http://www.arin.net/registration/asn/index.html
HTH..rate if helpful..
