All those born on 3, 12, 21 or 30 of any month come under numerology 3 and are dominated by number 3. The number 3 is the child, the result of the union of two opposite polarities number 1 and 2.

As a child, this number is very lighthearted and ready to play. It is strongly associated with creativity and imagination. It is motivating force filled with essence and synthesis. All thoughts and sources of imagination come through this number.

Since number one is considered absolute, number three is the first number identified fully as masculine. It is strongly associated with the natural element of air, which is impossible to see and hold yet felt everywhere in the natural environment. Everyone needs air and depends on it, but no one can really pick it up or play with it. That is the essence of the number three.
The characteristics of numerology 3 will be same as described in this page-

General Characteristics– The general characteristics of numerology three persons are of high self esteem and full of vigor and spirit. They dress well, love and like to take a leading part in social organizations. They have wide circle of friends and Strong desire for peace and harmony.

Strength– Cheerfulness, good luck, happiness, clever, confidence,and ambitious.

Weakness– Moody, loose talks, unforgiving nature.

Opportunity– Name and fame, overseas trips for higher studies, success in business.

Threat– Monetary loss in business and possibility of being cheated if not cautious. Too shy to reveal talent due to lack of self confidence.

Health – Liable to suffer from chest disorders, throat infections, sudden fever, and rheumatic trouble.

Finance– This is a lucky number for finance. Life is comfortable.One Should not lend money without security,this is fortunate number for business, finance and industry.

Compatible numbers for relation– 3, 6, 9.

Attractive numbers-3, 5, 6, 7, 9.

Repulsive numbers– 4, 8.

Influenced by– Number 3 persons are influenced by Jupiter.

Development comes in the year– 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 42, 45, 48, 51, 54, 57, 60, 63.

Lucky numbers– 1, 3, 9.

Unlucky numbers– 2,4,5,6,7, 8.

Lucky color– Yellow.

Gem– Yellow pushy rag.