137

the number 137 appears in various situations.

in mathematics, 137 is a prime number.

in the periodic table, Cs 137 can be found.

in physics, we have the fine-structure constant, 

~ 1/137.

the formula converting becquerel　into Sv is

x[mSv/year] = m[kg] × a[Bq] × 1/137.

where x is the annual radiation dose,m is the mass of radioactive material,

a is the activity of a quantity of the mass. 

the age of our universe is around 13.7 billion.