25681 has 4 divisors (see below), whose sum is σ = 26164. Its totient is φ = 25200.

The previous prime is 25679. The next prime is 25693. The reversal of 25681 is 18652.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 400 + 25281 = 20^2 + 159^2 .

It is a cyclic number.

It is not a de Polignac number, because 25681 - 2¹ = 25679 is a prime.

It is a super-2 number, since 2×25681² = 1319027522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (25601) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 150 + ... + 271.

It is an arithmetic number, because the mean of its divisors is an integer number (6541).

2²⁵⁶⁸¹ is an apocalyptic number.

It is an amenable number.

25681 is a deficient number, since it is larger than the sum of its proper divisors (483).

25681 is an equidigital number, since it uses as much as digits as its factorization.

25681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 482.

The product of its digits is 480, while the sum is 22.

The square root of 25681 is about 160.2529250903. The cubic root of 25681 is about 29.5033032785.

It can be divided in two parts, 256 and 81, that multiplied together give a 4-th power (20736 = 12⁴).

The spelling of 25681 in words is "twenty-five thousand, six hundred eighty-one".