Passing -a shows you the AS (autonomous system) number:

$ traceroute -a fmi.uni-sofia.bg
traceroute to fmi.uni-sofia.bg (62.44.101.138), 64 hops max, 40 byte packets
 1  [AS0] 10.0.0.1 (10.0.0.1)  0.460 ms  0.271 ms  0.256 ms
 2  [AS34224] 87.120.206.93.neterra.net (87.120.206.93)  0.871 ms  59.517 ms  1.989 ms
 3  [AS5421] border-lozenets.uni-sofia.bg (62.44.96.249)  1.186 ms  1.205 ms  1.342 ms
 4  [AS5421] fmi-gw.uni-sofia.bg (62.44.127.15)  1.354 ms  1.669 ms  1.509 ms
 5  [AS5421] www.fmi.uni-sofia.bg (62.44.101.138)  1.507 ms  1.698 ms  1.865 ms