What do you call the number on the right side of a decimal?

Collectively the 'decimal digits'.

Individually from the decimal point, and moving to the right;-

Tenths 0.1

Hundredths 0.01

Thousandths 0.001

Tens of Thousandths 0.0001

Hundreds of thousandths 0.00001

Millionths 0.000001

NB Note the use of the suffix '---ths'.

NNB Examples of how a decimal digit looks.