In western culture the number 13 is seen as unlucky. Friday 13th is seen as an unlucky day. Most high rise building do not have a 13th floor. They skip straight from 12 to 14.
In Sikhism the number 13 has a special meaning. The word for 13 in Panjabi is ‘tera’. This is the same word that is used for the word ‘yours’, as in everything is yours (Gods). Guru Nanak Dev Ji illustrated this when working at a shop. When measuring out quantities of food he got to the number 13 and then continued to recite the word ‘tera’ to show that everything is tera / yours / Gods.