Is 445 a prime number?

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

For 445, the answer is: No, 445 is not a prime number.

The list of all positive divisors (i.e., the list of all integers that divide 445) is as follows: 1, 5, 89, 445.

For 445 to be a prime number, it would have been required that 445 has only two divisors, i.e., itself and 1.

Find out more:

What is a prime number?

Actually, one can immediately see that 445 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 445 is 5, so it is divisible by 5 and is therefore not prime.

As a consequence:

445 is a multiple of 1
445 is a multiple of 5
445 is a multiple of 89

For 445 to be a prime number, it would have been required that 445 has only two divisors, i.e., itself and 1.

However, 445 is a semiprime (also called biprime or 2-almost-prime), because it is the product of a two non-necessarily distinct prime numbers. Indeed, 445 = 5 x 89, where 5 and 89 are both prime numbers.

Is 445 a deficient number?

Yes, 445 is a deficient number, that is to say 445 is a natural number that is strictly larger than the sum of its proper divisors, i.e., the divisors of 445 without 445 itself (that is 1 + 5 + 89 = 95).

Parity of 445

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

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What is an even number?

Is 445 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 445 is about 21.095.

Thus, the square root of 445 is not an integer, and therefore 445 is not a square number.

What is the square number of 445?

The square of a number (here 445) is the result of the product of this number (445) by itself (i.e., 445 × 445); the square of 445 is sometimes called "raising 445 to the power 2", or "445 squared".

The square of 445 is 198 025 because 445 × 445 = 445² = 198 025.

As a consequence, 445 is the square root of 198 025.

Number of digits of 445

445 is a number with 3 digits.

What are the multiples of 445?

The multiples of 445 are all integers evenly divisible by 445, that is all numbers such that the remainder of the division by 445 is zero. There are infinitely many multiples of 445. The smallest multiples of 445 are:

0: indeed, 0 is divisible by any natural number, and it is thus a multiple of 445 too, since 0 × 445 = 0
445: indeed, 445 is a multiple of itself, since 445 is evenly divisible by 445 (we have 445 / 445 = 1, so the remainder of this division is indeed zero)
890: indeed, 890 = 445 × 2
1 335: indeed, 1 335 = 445 × 3
1 780: indeed, 1 780 = 445 × 4
2 225: indeed, 2 225 = 445 × 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 445). 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 21.095). 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 445

Preceding numbers: …443, 444
Following numbers: 446, 447…

Nearest numbers from 445

Preceding prime number: 443
Following prime number: 449