A prime number is a whole number greater than 1 whose only factors are 1 and itself.

Factors of 5 are 1, 5

Factors of 11 are 1, 11

Factors of 21 are 1, 3, 7, 21

Factors of 37 are 1, 37.

Hence, according to the definition of a prime number, 21 is not a prime number as it has more than two factors.

The Holocaust, also referred to as the Shoah,[b] was a genocide during World War II in which Nazi Germany, aided by its collaborators, systematically murdered approximately 6 million European Jews, around two-thirds of the Jewish population of Europe, between 1941 and 1945.

The Holocaust originated in Nazi Germany in the late 1930s and eventually spread throughout Central and Eastern Europe into countries invaded and occupied by Germany during World War II.

The Nazis were racists and believed their race was more important. Nazis believed that the jews were a problem. Many of the non-germans that were living on the land were sent to concentration camps.

The main place it took place was eastern Germany and Poland. The Holocaust was largely comprised of a vast network of concentration camps in countries including Germany, Poland, Austria, Ukraine, Norway, the Czech Republic, Slovakia, Belarus, the Netherlands, and France.

Squirrels typically build leaf nests in the summer by weaving together small branches they've gnawed off of trees. These nests are lined with grass, moss, leaves and pine needles. Both male and female gray squirrels of all ages participate in building dens.
 

Meteorology is the study of weather and Earth's atmosphere. Climatology is another term used to describe the study of weather.

Studying the weather is not only useful for determining if you'll need an umbrella for the day. While forecasting is an important aspect of studying weather, understanding weather patterns provides valuable information about the status of the planet.

A respirometer is a device used to measure the rate of respiration of a living organism by measuring its rate of exchange of oxygen and/or carbon dioxide.

DPT refers to a class of combination vaccines against three infectious diseases in humans: diphtheria, pertussis, and tetanus.

Pertussis refers to whooping cough.