If all the six digit numbers \( x_1x_2x_3x_4x_5x_6 \) with \( 0 < x_1 < x_2 < x_3 < x_4 < x_5 < x_6 \) are arranged in the increasing order, then the sum of the digits in the \( 72^{\text{th}} \) number is ________.