Q: What number is a factor of any number whose digits add up to 3 or a multiple of 3?

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The number is 85.

A number ending in 0 or 5, whose digits sum to a multiple of 3.

An even number whose digits add up to 9 or a multiple of 9.

The divisibility test for the number 9 is: Any number whose digits add up to 9 or a multiple of 9, is divisible by 9. Any other number the sum of whose digits do not add up to 9 or a multiple of 9, are not divisible by 9.For example, the digits of 81 sum up to 9, and therefore, 81 is divisible by 9. The digits of the number 319381482 add up to 39, and therefore, 319381482 is divisible by 9.

52 is a number whose digits have a product of 10.

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Any number whose sum of its digits are equal to a multiple of 3, is divisible by 3. In this instance, the sum of the digits of the number 34215 is equal to 15, which is divisible by 3, and therefore the number is divisible by 3.

Any number whose digits add up to a multiple of 3 is divisible by 3. Since the digits of 990 add up to 18, this is a multiple of 3.The sum itself: 990 / 3 = 330

Answer 18. The two digit numbers less than 50 whose digits add to 9 are 45, 36, 27 and 18. 36 and 18 are even. 36 is the only number whose paired factor with 2 is even (18).

Any number whose digits add up to 9 is also a multiple of 9 as for example 162 is 1+6+2 = 9 and 9*18 = 162

The largest 3 digit number whose digits are all primes is 777. The largest 3 digit number with different prime digits is 753.

The largest three digit prime number whose digits are all primes is 773.

Find a four digit number whose digits will be reversed when multiplied by nine?

64

64

There is no such number. If the four digits are even, the entire number is even, not odd.

23

279,999,720

66

1

The answer is 66.

18

18

17

The sum of the digits of the number will add to a number that's divisible by nine. For example, 99 -> 9+9 -> 18. 18 is divisible by nine, thus 99 is. Any whole number that's divisible by nine will have its digits add up like this, and any whole number whose digits add up like this will be divisible by nine.