Warning: Explicit integral could not be found

symb x1  x2
numerator =
6912*pi^2*x1*x2*exp(-(2329462948656273*((1767233828455439*x1^4)/288230376151711744)^(1/2))/4398046511104)*exp(-24*pi*x1^2)*exp(-72*pi*x2^2)

N1=int(numerator,x1,0,inf);
N=int(N1,x2,0,inf);

i make double integeration on x1,x2 from 0 to infinity. the message appears even i made for one variable integeral x can any body help me and tell me where is my error

[Walter Roberson]

Interestingly, there is an explicit integral for each of the parts. The final result is

N = 18889465931478580854784 * pi / (776487649552091 * sqrt(1767233828455439) + 18889465931478580854784 * pi)