Is 77 a prime number?
It is possible to find out using mathematical methods whether a given integer is a prime number or not.
For 77, the answer is: No, 77 is not a prime number.
The list of all positive divisors (i.e., the list of all integers that divide 77) is as follows: 1, 7, 11, 77.
For 77 to be a prime number, it would have been required that 77 has only two divisors, i.e., itself and 1.
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As a consequence:
For 77 to be a prime number, it would have been required that 77 has only two divisors, i.e., itself and 1.
However, 77 is a semiprime (also called biprime or 2-almost-prime), because it is the product of a two non-necessarily distinct prime numbers. Indeed, 77 = 7 x 11, where 7 and 11 are both prime numbers.
Is 77 a deficient number?
Yes, 77 is a deficient number, that is to say 77 is a natural number that is strictly larger than the sum of its proper divisors, i.e., the divisors of 77 without 77 itself (that is 1 + 7 + 11 = 19).