25640 has 16 divisors (see below), whose sum is σ = 57780. Its totient is φ = 10240.

The previous prime is 25639. The next prime is 25643. The reversal of 25640 is 4652.

It can be written as a sum of positive squares in 2 ways, for example, as 24964 + 676 = 158^2 + 26^2 .

It is not an unprimeable number, because it can be changed into a prime (25643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 281 + ... + 360.

2²⁵⁶⁴⁰ is an apocalyptic number.

25640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

25640 is an abundant number, since it is smaller than the sum of its proper divisors (32140).

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

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28890).

25640 is a wasteful number, since it uses less digits than its factorization.

25640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 652 (or 648 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 25640 is about 160.1249512100. The cubic root of 25640 is about 29.4875941324.

The spelling of 25640 in words is "twenty-five thousand, six hundred forty".