In the Bible, the number seven (sheva) connotes a sense of abundance and is the root of the word sova, which means fullness. Abraham ibn Ezra (on Leviticus 26:18) cites seven’s status as a prime number as the reason for its link with bountifulness.
Likewise, the number 70 (shivi’im) embodies fullness and infinity. There are many biblical seventies; 70 souls who descended to Egypt (Genesis 46:27); 70 elders who, together with Moses (Numbers 11:16), ruled over the Israelites in the desert; and 70 years of the Babylonian exile. In the Talmud, the rabbis credit Mordecai with knowledge of 70 languages (shivi’im lashon), corresponding to the 70 nations of the world (shivi’im umot), which had a Temple sacrifice of 70 cows offered during Succot in their honour. Best known is perhaps the “shivi’im panim [70 faces] to the Torah”, meaning that we can interpret the Torah in an infinite number of ways.
Today, shivi’im is trifling amount compared to the reigning big numbers of billion and trillion. The world in which shivi’im could conjure up images of limitlessness is far behind us.