No.
It is prime.
991 is a prime, the others are composite.
The positive integer factors of 991 are: 1, 991
1 and 991
991 and 1.991 is a prime number and only has factors of 1 and 991.
0.0091
sqrt(991) = 31.480 (to 5 sf)
991 is a prime and so has no proper factors.
991 is already prime. No tree is required.
To find what must be subtracted from 991 to get 479, you can set up the equation: 991 - x = 479. By rearranging it, you find that x = 991 - 479. Therefore, 512 must be subtracted from 991 to get 479.
76.2308
Yes, 991 is a prime number. It has no factors other than 1 and itself.