25781 has 8 divisors (see below), whose sum is σ = 30720. Its totient is φ = 21168.

The previous prime is 25771. The next prime is 25793. The reversal of 25781 is 18752.

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

It is not a de Polignac number, because 25781 - 2⁶ = 25717 is a prime.

It is a super-2 number, since 2×25781² = 1329319922, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a nialpdrome in base 13.

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 25781.

It is not an unprimeable number, because it can be changed into a prime (25741) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 140 + ... + 266.

It is an arithmetic number, because the mean of its divisors is an integer number (3840).

2²⁵⁷⁸¹ is an apocalyptic number.

It is an amenable number.

25781 is a deficient number, since it is larger than the sum of its proper divisors (4939).

25781 is a wasteful number, since it uses less digits than its factorization.

25781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 163.

The product of its digits is 560, while the sum is 23.

The square root of 25781 is about 160.5646287325. The cubic root of 25781 is about 29.5415482732.

The spelling of 25781 in words is "twenty-five thousand, seven hundred eighty-one".