The great Imam Abu Hanifah An-Nu^man said in Al-Fiqh Al-Akbar:
The basis of Tawhid and what constitutes a valid belief is for one to say I believe in Allah, His Angels, His Books, His Messengers, Resurrection after death, Destiny both good and evil and that it is created by Allah, the Settlement of Accounts on the Day of Judgment, the Balance, Paradise and Hellfire. All are true matters.
Allah, the Exalted, is One not in the context of numbers but with the meaning that He has no partners.
Click on this text to view Al Fiqh Akbar in PDF