5645 has 4 divisors (see below), whose sum is σ = 6780. Its totient is φ = 4512.

The previous prime is 5641. The next prime is 5647. The reversal of 5645 is 5465.

5645 = T₄₅ + T₄₆ + ... + T₄₉.

5645 is nontrivially palindromic in base 2.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5465 = 5 ⋅1093.

It can be written as a sum of positive squares in 2 ways, for example, as 1156 + 4489 = 34^2 + 67^2 .

It is a cyclic number.

It is not a de Polignac number, because 5645 - 2² = 5641 is a prime.

It is a super-3 number, since 3×5645³ = 539651133375, which contains 333 as substring.

It is a nialpdrome in base 9.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 5645.

It is not an unprimeable number, because it can be changed into a prime (5641) by changing a digit.

It is an upside-down number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 560 + ... + 569.

It is an arithmetic number, because the mean of its divisors is an integer number (1695).

It is an amenable number.

5645 is a deficient number, since it is larger than the sum of its proper divisors (1135).

5645 is a wasteful number, since it uses less digits than its factorization.

5645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1134.

The product of its digits is 600, while the sum is 20.

The square root of 5645 is about 75.1332150250. The cubic root of 5645 is about 17.8055194767.

Adding to 5645 its sum of digits (20), we get a palindrome (5665).

Subtracting from 5645 its sum of digits (20), we obtain a square (5625 = 75²).

It can be divided in two parts, 56 and 45, that added together give a palindrome (101).

The spelling of 5645 in words is "five thousand, six hundred forty-five".