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 Nov4 awarded Popular Question Mar15 comment Any natural number is greater than or equal to its product of digits. What do you mean? The number 4 is 4 * 10^0. Applying a function like multiplication on its digits simply returns itself, since there's nothing really to do. But how does that fit in here? Mar15 comment Any natural number is greater than or equal to its product of digits. Looking at the logic above, we see that if our number is larger than 10, it contains multipliers greater than a possible digit. So for a number to be equal to the product of its digits, it must not have this behaviour. Which numbers have only digit-possible multiplications? Single digit numbers. Mar15 awarded Editor Mar15 awarded Teacher Mar15 comment Any natural number is greater than or equal to its product of digits. @mirdul Thanks! Corrected. Mar15 revised Any natural number is greater than or equal to its product of digits. edited body Mar15 answered Any natural number is greater than or equal to its product of digits. Sep9 comment What are some examples of mathematics that had unintended useful applications much later? There's a story that in 1897, after discovering the electron, the researchers celebrated and said "here's to the electron, a particle nobody will care about". Dec30 awarded Scholar Dec30 awarded Supporter Dec30 accepted Parallelogram trigonometry Jan5 awarded Nice Question Dec4 awarded Student Dec4 asked Parallelogram trigonometry Aug27 awarded Autobiographer