The largest one digit number that has three factors is 9. Its factors are 1, 3, and 9.
49
97
If factors include 1 and the number itself then the any number (n) with only 4 factors has to be the product of two prime numbers, p1 and p2. The factors are then n, p1, p2, and 1. The largest 3-digit number with only 4 factors is 998. The factors are 998, 499, 2 and 1
35 x 285 = 9975 The highest three-digit number divisible by 35 is 9975.
9409
95
997
81
The largest one digit number that has three factors is 9. Its factors are 1, 3, and 9.
How about 99 whose factors are: 1, 3, 9, 11 33 and 99
The best way to tackle this is to take the largest 3 digit number (999) and work out its prime factors. You can then work down until you get one with exactly five prime factors. 999 is 3x3x3x37, 998 is 2x499, 997 is prime, 996 is 2x2x3x83, 995 is 5x199, 994 is 2x7x71, 993 is 3x331, 992 is 2x2x2x2x2x31, 991 is prime, 990 is 2x3x3x5x11. That is the first we came across with five prime factors. Therefore the largest 3 digit number with exactly five prime factors is 990.
97
I think you mean, the largest four digit number that has exactly three divisors. 2X3X1663=9,978
36 has nine factors.
625 has five factors.
64