1, 3, 9, 71, 213, 639
Six factors.
639 is a composite number. Its positive integer factors are: 1, 3, 9, 71, 213, 639
1, 639 Then by inspection of the number 639 , we note that each number is a multiple of '3' . So '3' is a factor. Also , slightly more 'tricky'. If we add the digits of 639 ; 6 + 3 + 9 = 18 1 + 8 = 9 . This means that the number has '9' is a factor. NB This only applies to factors/multiples of '9' Finally, divide 639 by 71 and/or 213 . If you have a whole number answer (No decimals), then those numbers are also factors of 639. Hence 639/71 = 9 & 329 / 213 = 3 So allthe given numbers are factors of 639.
3 x 3 x 71 are the prime factors. You should now be able to calculate the composites...
1, 3, 9, 27, 71, 213, 639, 1917
The factors of 1,278 are: 1 2 3 6 9 18 71 142 213 426 639 1278
The factors of 1278 are: 1, 2, 3, 6, 9, 18, 71, 142, 213, 426, 639, 1278
The factors of 1,278 are: 1 2 3 6 9 18 71 142 213 426 639 1,278
Separate the number into prime factors. Then it should be easy to get ALL the factors, simply by combining different prime factors.
639 ÷ 3 = 213
The factors of 1278 are: 1, 2, 3, 6, 9, 18, 71, 142, 213, 426, 639, 1278.
639 divided by 3 = 213 So 213 x 3 = 639