God is Satchidananda: Existence Absolute, Knowledge Absolute and Bliss Absolute.
God is Antaryamin: He is the Inner Ruler of this body and mind. He is omnipotent, omniscient and omnipresent.
God is Chiranjeevi: He is permanent, eternal, perpetual, indestructible, immutable and imperishable. God is past, present and future. He is unchanging amidst the changing phenomena.
God is Paramatma: He is the Supreme Being. The Bhagavad Gita styles Him as 'Purushottama' or Supreme Purusha or Maheswara.
God is Sarva-vid: He is ever-knowledgeable. He knows everything in detail. He is 'Swasamvedya', that is, he knows by Himself.
God is Chirashakti: He is ever-powerful. Earth, water, fire, air and ether are His five powers. 'Maya' is His illusive Shakti (power).
God is Swayambhu: He is self-existent. He does not depend upon others for His existence. He is 'Swayam Prakasha' or self-luminous. He reveals Himself by His own light.
God is Swatah Siddha: He is self-proven. He does not want any proof, because He is the basis for the act or process of proving. God is 'Paripoorna' or self-contained.
God is Swatantra: He is Independent. He has good desires ('satkama') and pure will ('satsankalpa').
God is Eternal Happiness: Supreme Peace can be had only in God. God-realisation can bestow supreme happiness on humankind.
God is Love: He is an embodiment of eternal bliss, supreme peace and wisdom. He is all-merciful, omniscient, omnipotent and omnipresent.
God is Life: He is the 'Prana' (life) in the body and intelligence in 'Antahkarana' (fourfold mind: mind, intellect, ego and the subconscious mind).
God has 3 Aspects: Brahma, Vishnu and Shiva are the three aspects of God. Brahma is the creative aspect; Vishnu is the preservative aspect; and Shiva is the destructive aspect.
God has 5 Activities: 'Srishti' (creation), 'Sthiti' (preservation), 'Samhara' (destruction), 'Tirodhana' or 'Tirobhava' (veiling), and 'Anugraha' (grace) are the five kinds of activities of God.
God has 6 Attributes of Divine Wisdom or 'Gyana': 'Vairagya' (dispassion), 'Aishwarya' (powers), 'Bala' (strength), 'Sri' (wealth) and 'Kirti' (fame).
God Lives in You: He dwells in the chamber of your own heart. He is the silent witness of your mind. This body is His moving temple. The 'sanctum sanctorum' is the chamber of your own heart. If you cannot find Him there, you cannot find Him anywhere else.
Swami Sivananda in his book 'God Exists' describes the essential properties of Brahman - the absolute almighty. Here's a simplified excerpt.