My version of Number of the Day has been adapted from something that a colleague showed me about 5 years ago.
I find this to be a very effective starter activity for a Maths lesson. Students are expected to complete a range of different questions using a particular number as their starting point. The questions cover aspects which would probably be considered as 'basic' number skills - the sorts of things that I want my students to be really confident about.
The teacher can choose to include all of the questions or just some by ticking the small boxes.
The teacher also chooses the Number of the Day - I often use the date although the beginning of each month is rather less interesting!
For me, the real strength of this activity is the almost endless differentiation.
For example, students could be asked to add, subtract, multiply or divide integers or decimals or negative numbers. Students may need to make an estimate of the square root if it is not an integer. Students could be asked to find 50% or 35% or 1.5% of the number. Students could be asked to find 1/2 or 3/5 or 8/11 of the number. You get the idea...!
Additionally, the Number of the Day itself can be chosen to make the questions easier or harder.
If you'd like to try this starter out for yourself, you can find the PowerPoint file here.