There are 3 kinds of kappas - namely, antara kappa, asankheyya kappa, and maha kappa. 
The interim period when the age limit of human beings arises from ten to an indefinite  time and then falls to ten again, is known as an antara kappa. 

Twenty such antara kappa equal one asankheyya kappa, literally - an incalculable cycle. 
Four asankheyya kappas equal one maha kappa. 

Books state that 50 human years equal one celestial day. The age-limit of gods of the realm of Four Kings is 500 celestial years, that is, according to human cycle reckoning  9,000,000. 
 

Four Modes Of Birth

Buddhism states that there are four modes of birth - namely :

    1.   egg-born beings (andaja), 
 
    2.   womb-born beings (jalabuja), 
 
    3.   moisture-born beings (samsedaja) 
 
    4.   beings having spontaneous births (opapatika).

This broad classification embraces the 4 modes of birth of all living beings.

Birds and oviparous snakes belong to the first division.

The womb-born creatures comprise all human beings, some devas inhabiting the earth, 
and some animals that take conception in a mother’s womb.

Embryos, using moisture as nidus for their growth, like certain lowly forms of animal life, 
belong to the third class.

Beings having a spontaneous birth are generally invisible to the physical eye. 
Conditioned by their past Kamma, they appear spontaneously, 
without passing through an embryonic stage. 
Petas and Devas normally, and Brahmas belong to this class.
 

Four Ways Body Is Affected

Our body can be affected by the following 4 conditions: 

    1.   Food
 
    2.   Weather 
 
    3.   Mind
 
    4.   Kamma