%I
%S 1147,1159,1189,1343,1711,1943,1961,2911,2923,3713,4171,4183,4189,
%T 4307,4331,4717,5329,5917
%N Fourdigit semiprimes that are concatenation and product of two 2digit primes.
%C There are 18 such integers:
%C 1147=31*37,1159=19*61,1189=29*41,1343=17*79,1711=29*59,1943=29*67,
%C 1961=37*53,2911=41*71,2923=37*79,3713=47*79,4171=43*97,4183=47*89,
%C 4189=59*71,4307=59*73,4331=61*71,4717=53*89,5329=73*73,5917=61*97.
%C Two particularly interesting cases:
%C 1159=19*61=> 1961=37*53, 2911=41*71 =>4171=43*97.
%e 1147 = concatenation of primes 11 and 47 and product of primes 31 and 37.
%K base,fini,full,nonn
%O 1,1
%A _Zak Seidov_, Jan 18 2011
