Is 105 a prime number?
It is possible to find out using mathematical methods whether a given integer is a prime number or not.
For 105, the answer is: No, 105 is not a prime number.
The list of all positive divisors (i.e., the list of all integers that divide 105) is as follows: 1, 3, 5, 7, 15, 21, 35, 105.
For 105 to be a prime number, it would have been required that 105 has only two divisors, i.e., itself and 1.
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Actually, one can immediately see that 105 cannot be prime, because 5 is one of its divisors: indeed, a number ending with 0 or 5 has necessarily 5 among its divisors. The last digit of 105 is 5, so it is divisible by 5 and is therefore not prime.
As a consequence:
- 105 is a multiple of 1
- 105 is a multiple of 3
- 105 is a multiple of 5
- 105 is a multiple of 7
- 105 is a multiple of 15
- 105 is a multiple of 21
- 105 is a multiple of 35
For 105 to be a prime number, it would have been required that 105 has only two divisors, i.e., itself and 1.
Is 105 a deficient number?
Yes, 105 is a deficient number, that is to say 105 is a natural number that is strictly larger than the sum of its proper divisors, i.e., the divisors of 105 without 105 itself (that is 1 + 3 + 5 + 7 + 15 + 21 + 35 = 87).