25840 has 40 divisors (see below), whose sum is σ = 66960. Its totient is φ = 9216.

The previous prime is 25819. The next prime is 25841. The reversal of 25840 is 4852.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (19).

25840 is an undulating number in base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (25841) by changing a digit.

25840 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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, 1351 + ... + 1369.

It is an arithmetic number, because the mean of its divisors is an integer number (1674).

2²⁵⁸⁴⁰ is an apocalyptic number.

25840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 25840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33480).

25840 is an abundant number, since it is smaller than the sum of its proper divisors (41120).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

25840 is a wasteful number, since it uses less digits than its factorization.

With its predecessor (25839) it forms a Ruth-Aaron pair, since the sum of their distinct prime factors is the same (43).

25840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49 (or 43 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 19.

The square root of 25840 is about 160.7482503793. The cubic root of 25840 is about 29.5640664514.

The spelling of 25840 in words is "twenty-five thousand, eight hundred forty".