5781 has 8 divisors (see below), whose sum is σ = 8064. Its totient is φ = 3680.

The previous prime is 5779. The next prime is 5783. The reversal of 5781 is 1875.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (5779) and next prime (5783).

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

It is a cyclic number.

It is not a de Polignac number, because 5781 - 2¹ = 5779 is a prime.

It is a super-2 number, since 2×5781² = 66839922, which contains 22 as substring.

It is a plaindrome in base 7.

It is a zygodrome in base 4.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (5783) 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, 100 + ... + 146.

It is an arithmetic number, because the mean of its divisors is an integer number (1008).

2⁵⁷⁸¹ is an apocalyptic number.

5781 is the 41-st nonagonal number.

It is an amenable number.

5781 is a deficient number, since it is larger than the sum of its proper divisors (2283).

5781 is a wasteful number, since it uses less digits than its factorization.

5781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91.

The product of its digits is 280, while the sum is 21.

The square root of 5781 is about 76.0328876211. The cubic root of 5781 is about 17.9473771718.

The spelling of 5781 in words is "five thousand, seven hundred eighty-one".