Is 100 a prime number?
It is possible to find out using mathematical methods whether a given integer is a prime number or not.
For 100, the answer is: No, 100 is not a prime number.
The list of all positive divisors (i.e., the list of all integers that divide 100) is as follows: 1, 2, 4, 5, 10, 20, 25, 50, 100.
For 100 to be a prime number, it would have been required that 100 has only two divisors, i.e., itself and 1.
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Actually, one can immediately see that 100 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 100 is 0, so it is divisible by 5 and is therefore not prime.
As a consequence:
- 100 is a multiple of 1
- 100 is a multiple of 2
- 100 is a multiple of 4
- 100 is a multiple of 5
- 100 is a multiple of 10
- 100 is a multiple of 20
- 100 is a multiple of 25
- 100 is a multiple of 50
For 100 to be a prime number, it would have been required that 100 has only two divisors, i.e., itself and 1.
Is 100 a deficient number?
No, 100 is not a deficient number: to be deficient, 100 should have been such that 100 is larger than the sum of its proper divisors, i.e., the divisors of 100 without 100 itself (that is 1 + 2 + 4 + 5 + 10 + 20 + 25 + 50 = 117).
In fact, 100 is an abundant number; 100 is strictly smaller than the sum of its proper divisors (that is 1 + 2 + 4 + 5 + 10 + 20 + 25 + 50 = 117). The smallest abundant number is 12.