20945 has 8 divisors (see below), whose sum is σ = 25920. Its totient is φ = 16240.

The previous prime is 20939. The next prime is 20947. The reversal of 20945 is 54902.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20945 - 2⁴ = 20929 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20947) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 260 + ... + 330.

It is an arithmetic number, because the mean of its divisors is an integer number (3240).

2²⁰⁹⁴⁵ is an apocalyptic number.

It is an amenable number.

20945 is a deficient number, since it is larger than the sum of its proper divisors (4975).

20945 is an equidigital number, since it uses as much as digits as its factorization.

20945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 135.

The product of its (nonzero) digits is 360, while the sum is 20.

The square root of 20945 is about 144.7238750172. The cubic root of 20945 is about 27.5651348599.

The spelling of 20945 in words is "twenty thousand, nine hundred forty-five".