numbers divisible by 4

[xavier]

what is a rule for numbers divisible by 4, 8 and 9

[hobbitess]

Multiples of 72 ???????

[hobbitess]

Wrong answer!!

[johnalex]

Numbers divisible by 9 add up to 9. eg 54, 81, 333, 801, 735264986421321 = 63 = 9, etc

[johnalex]

If the last two digits of a number are divisible by 4 then the entire number is divisible by 4. eg 356, 7116, 91072

[biley]

If you mean what is a rule for numbers divisible by all three numbers - 4 8 and 9 - then hobbitess surely has the only answer possible - the number must be divisible by 72 (or multiples of 72 in other words).

[johnalex]

In which case, for a number to be divisible by 72 then the above rule for 9 would still apply and additionally the last 3 digits must be divisible by 8.

e.g. 49335624 is divisible by 72, because:

4+9+3+3+5+6+2+4 = 36, (3 + 6 = 9)

and 624 (last three digits) are divisible by 8

Hope this helps Xavier (your question was slightly ambiguous). I presume you are looking for a quick recognition method - this system requires two stages. Maybe there's a faster one ?