Is 7 divisible by 7321694

Answer 1

No; 7 is less than 7321694 so it cannot be divisible by it.

Nor is 7321694 divisible by 7.

There is no easy test for divisibility by 7 - most tests devised take just as long if not longer than dividing the original number by 7.

One test I can offer:

1) Write the number in blocks of 3 digits from the right hand end (just like when writing out big numbers);

2) For each of the 3 digits in the blocks, alternatively subtract and add starting from the right hand end. If any digit is missing from the first block, it is taken as zero;

3) add twice the sum of the first ("hundreds) digit to three times the sum of the second ("tens") digit to the sum of the third ("ones") digit;

4) if this sum is divisible by 7 then so is the original number.

For 7321694 this gives:

1) 7 321 694

2) first digits: 6 - 3 = 3, second digits: 9 - 2 = 7, third digits:4 - 1 + 7 = 10

3) 2x3 + 3x7 + 10 = 37.

4) 37 is not divisible by 7, so 7321694 is not divisible by 7.