Is 691 a prime number?
It is possible to find out using mathematical methods whether a given integer is a prime number or not.
For 691, the answer is: yes, 691 is a prime number because it has only two distinct divisors: 1 and itself (691).
As a consequence, 691 is only a multiple of 1 and 691.
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Since 691 is a prime number, 691 is also a deficient number, that is to say 691 is a natural integer that is strictly larger than the sum of its proper divisors, i.e., the divisors of 691 without 691 itself (that is 1, by definition!).