Is 145 a prime number?

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

For 145, the answer is: No, 145 is not a prime number.

The list of all positive divisors (i.e., the list of all integers that divide 145) is as follows: 1, 5, 29, 145.

For 145 to be a prime number, it would have been required that 145 has only two divisors, i.e., itself and 1.

Find out more:

What is a prime number?

Actually, one can immediately see that 145 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 145 is 5, so it is divisible by 5 and is therefore not prime.

As a consequence:

145 is a multiple of 1
145 is a multiple of 5
145 is a multiple of 29

For 145 to be a prime number, it would have been required that 145 has only two divisors, i.e., itself and 1.

However, 145 is a semiprime (also called biprime or 2-almost-prime), because it is the product of a two non-necessarily distinct prime numbers. Indeed, 145 = 5 x 29, where 5 and 29 are both prime numbers.

Is 145 a deficient number?

Yes, 145 is a deficient number, that is to say 145 is a natural number that is strictly larger than the sum of its proper divisors, i.e., the divisors of 145 without 145 itself (that is 1 + 5 + 29 = 35).

Parity of 145

145 is an odd number, because it is not evenly divisible by 2.

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What is an even number?

Is 145 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 145 is about 12.042.

Thus, the square root of 145 is not an integer, and therefore 145 is not a square number.

What is the square number of 145?

The square of a number (here 145) is the result of the product of this number (145) by itself (i.e., 145 × 145); the square of 145 is sometimes called "raising 145 to the power 2", or "145 squared".

The square of 145 is 21 025 because 145 × 145 = 145² = 21 025.

As a consequence, 145 is the square root of 21 025.

Number of digits of 145

145 is a number with 3 digits.

What are the multiples of 145?

The multiples of 145 are all integers evenly divisible by 145, that is all numbers such that the remainder of the division by 145 is zero. There are infinitely many multiples of 145. The smallest multiples of 145 are:

0: indeed, 0 is divisible by any natural number, and it is thus a multiple of 145 too, since 0 × 145 = 0
145: indeed, 145 is a multiple of itself, since 145 is evenly divisible by 145 (we have 145 / 145 = 1, so the remainder of this division is indeed zero)
290: indeed, 290 = 145 × 2
435: indeed, 435 = 145 × 3
580: indeed, 580 = 145 × 4
725: indeed, 725 = 145 × 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 145). 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 12.042). 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 145

Preceding numbers: …143, 144
Following numbers: 146, 147…

Nearest numbers from 145

Preceding prime number: 139
Following prime number: 149