the prince = ruler. Hebrew. sar = a ruler (from sarar = to rule). Hence Caesar, Tzar or Czar. Generally rendered "prince" in this book. See Dan_1:7, Dan_1:8, Dan_1:9, Dan_1:10, Dan_1:11, Dan_1:18; Dan_8:11, Dan_8:25; Dan_9:6, Dan_9:8; Dan_10:13, Dan_10:20, Dan_10:21; Dan_11:5; Dan_12:1. The rulers may be good, angelic (good or evil), or the world-rulers of Eph_6:12.
withstood = was standing confronting me.
one and twenty days. See verses: Dan_10:2, Dan_10:3.
Michael = who is like GOD (Hebrew El)? The second angel named in this book. The special angelic ruler for Israel (Dan_10:21; Dan_12:1. Compare Jud_1:9, and Rev_12:7).
princes. Hebrew. sar = chief. Not the same word as in Dan_11:8, Dan_11:18, Dan_11:22.
I remained = I was superfluous: i.e. not needed. Hence we may render, "I left him there". Not the same word as in Dan_10:17.