20745 has 12 divisors (see below), whose sum is σ = 36036. Its totient is φ = 11040.

The previous prime is 20743. The next prime is 20747. The reversal of 20745 is 54702.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (20743) and next prime (20747).

It can be written as a sum of positive squares in 2 ways, for example, as 7056 + 13689 = 84^2 + 117^2 .

It is not a de Polignac number, because 20745 - 2¹ = 20743 is a prime.

It is a Curzon number.

It is a plaindrome in base 14.

It is a zygodrome in base 14.

It is not an unprimeable number, because it can be changed into a prime (20743) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 186 + ... + 275.

It is an arithmetic number, because the mean of its divisors is an integer number (3003).

2²⁰⁷⁴⁵ is an apocalyptic number.

It is an amenable number.

20745 is a deficient number, since it is larger than the sum of its proper divisors (15291).

20745 is a wasteful number, since it uses less digits than its factorization.

20745 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 472 (or 469 counting only the distinct ones).

The product of its (nonzero) digits is 280, while the sum is 18.

The square root of 20745 is about 144.0312466099. The cubic root of 20745 is about 27.4771159486.

Adding to 20745 its product of nonzero digits (280), we get a square (21025 = 145²).

It can be divided in two parts, 207 and 45, that added together give a palindrome (252).

The spelling of 20745 in words is "twenty thousand, seven hundred forty-five".