20445 has 16 divisors (see below), whose sum is σ = 34560. Its totient is φ = 10304.

The previous prime is 20443. The next prime is 20477. The reversal of 20445 is 54402.

It is a cyclic number.

It is not a de Polignac number, because 20445 - 2¹ = 20443 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (15).

20445 is an undulating number in base 12.

20445 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20441) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 412 + ... + 458.

It is an arithmetic number, because the mean of its divisors is an integer number (2160).

2²⁰⁴⁴⁵ is an apocalyptic number.

It is an amenable number.

20445 is a deficient number, since it is larger than the sum of its proper divisors (14115).

20445 is a wasteful number, since it uses less digits than its factorization.

20445 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 84.

The product of its (nonzero) digits is 160, while the sum is 15.

The square root of 20445 is about 142.9860133020. The cubic root of 20445 is about 27.3440205415.

Adding to 20445 its reverse (54402), we get a palindrome (74847).

It can be divided in two parts, 204 and 45, that multiplied together give a triangular number (9180 = T₁₃₅).

The spelling of 20445 in words is "twenty thousand, four hundred forty-five".