What is the 17-character compound surname?

Which country are you talking about? There is no compound surname of 17 in China.

There are 8 1 compound surnames in China:

Ouyang, Taishi, Duanmu, Shangguan, Sima,

Dongfang, Dugu, Nangong, Wanxian, Wen Ren,

Xiahou, Zhuge, Wei Chi, Ram, Helian,

Dan Tai, Huangfu, Zong Zheng, Puyang, Ye Gong,

Uncle, Shen Tu, Gongsun, Murong,

Li Zhong, Sun Qiang, Yu Wen, Situ, Xian Yu,

Sikong, Lu Qiu, Ziche, Guan Qi, Scott,

Uma, Gong Xi, Zhuan Sun, loam, agricultural land,

Qi Diao, Lezheng, Zaifu, Gu Liang, Tuoba,

Keywords Oracle bones, Xuanyuan, Hu Ling, Duangan, Baili,

Keywords Huyan, Dongguo, South Gate, Yangtongge, Weisheng,

Gong Hu, Gong Yu, Gongyi, Liang Qiu, Gong Zhong,

Gong Shang, Gong Men, Gong Shan, Gong Jian, Zuo Qiu,

Gongbo, Ximen, Gong Zu, fifth, Miyagi,

Qiu Guan, Gong Xi, Nanrong, Dongli, Dongfang,

Zhongchang, Zishu, Sang Zi, Jimo, Daxi,

Chu Shi and Wu Ming.