Is 78 a prime number? What are the divisors of 78?

Is 78 a prime number?

It is possible to find out using mathematical methods whether a given integer is a prime number or not.

For 78, the answer is: No, 78 is not a prime number.

The list of all positive divisors (i.e., the list of all integers that divide 78) is as follows: 1, 2, 3, 6, 13, 26, 39, 78.

To be 78 a prime number, it would have been required that 78 has only two divisors, i.e., itself and 1.

As a consequence:

  • 78 is a multiple of 1
  • 78 is a multiple of 2
  • 78 is a multiple of 3
  • 78 is a multiple of 6
  • 78 is a multiple of 13
  • 78 is a multiple of 26
  • 78 is a multiple of 39

To be 78 a prime number, it would have been required that 78 has only two divisors, i.e., itself and 1.

Is 78 a deficient number?

No, 78 is not a deficient number: to be deficient, 78 should have been such that 78 is larger than the sum of its proper divisors, i.e., the divisors of 78 without 78 itself (that is 1 + 2 + 3 + 6 + 13 + 26 + 39 = 90).

In fact, 78 is an abundant number; 78 is strictly smaller than the sum of its proper divisors (that is 1 + 2 + 3 + 6 + 13 + 26 + 39 = 90). The smallest abundant number is 12.

Parity of 78

78 is an even number, because it is evenly divisible by 2: 78 / 2 = 39.

Is 78 a perfect square number?

A number is a perfect square (or a square number) if its square root is an integer; that is to say, it is the product of an integer with itself. Here, the square root of 78 is about 8.832.

Thus, the square root of 78 is not an integer, and therefore 78 is not a square number.

What is the square number of 78?

The square of a number (here 78) is the result of the product of this number (78) by itself (i.e., 78 × 78); the square of 78 is sometimes called "raising 78 to the power 2", or "78 squared".

The square of 78 is 6 084 because 78 × 78 = 782 = 6 084.

As a consequence, 78 is the square root of 6 084.

Number of digits of 78

78 is a number with 2 digits.

What are the multiples of 78?

The multiples of 78 are all integers evenly divisible by 78, that is all numbers such that the remainder of the division by 78 is zero. There are infinitely many multiples of 78. The smallest multiples of 78 are:

  • 0: indeed, 0 is divisible by any natural number, and it is thus a multiple of 78 too, since 0 × 78 = 0
  • 78: indeed, 78 is a multiple of itself, since 78 is evenly divisible by 78 (we have 78 / 78 = 1, so the remainder of this division is indeed zero)
  • 156: indeed, 156 = 78 × 2
  • 234: indeed, 234 = 78 × 3
  • 312: indeed, 312 = 78 × 4
  • 390: indeed, 390 = 78 × 5
  • etc.

How to determine whether an integer is a prime number?

To determine the primality of a number, several algorithms can be used. The most naive technique is to test all divisors strictly smaller to the number of which we want to determine the primality (here 78). First, we can eliminate all even numbers greater than 2 (and hence 4, 6, 8…). Then, we can stop this check when we reach the square root of the number of which we want to determine the primality (here the square root is about 8.832). Historically, the sieve of Eratosthenes (dating from the Greek mathematics) implements this technique in a relatively efficient manner.

More modern techniques include the sieve of Atkin, probabilistic algorithms, and the cyclotomic AKS test.

Numbers near 78

  • Preceding numbers: …76, 77
  • Following numbers: 79, 80

Nearest numbers from 78

  • Preceding prime number: 73
  • Following prime number: 79
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