Yes.
Yes, it is.
Yes.
22.8254244
It is: 1*521 = 521 which is a prime number
521 is a Prime Number.
It is a prime number
123 456 789
The mixed number of 52.001 is: 521/1000
It is: 2 and 521/1000
521
There is no easy test. You need to divide the number by all the primes up to the square root of the number, so if you want to know if 56789 is prime, you need to divide by all the prime numbers up to 239. If you go through all the primes up to the square root and don't get an even number as the result of the division then the number is prime. (Incidentally, the factors of 56789 are 109 and 521.)
808-521-2879