25642640 has 20 divisors (see below), whose sum is σ = 59619324. Its totient is φ = 10257024.

The previous prime is 25642621. The next prime is 25642649. The reversal of 25642640 is 4624652.

It can be written as a sum of positive squares in 2 ways, for example, as 7118224 + 18524416 = 2668^2 + 4304^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a Smith number, since the sum of its digits (29) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (25642649) 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, 160187 + ... + 160346.

Almost surely, 2^25642640 is an apocalyptic number.

25642640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

25642640 is an abundant number, since it is smaller than the sum of its proper divisors (33976684).

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

25642640 is a wasteful number, since it uses less digits than its factorization.

25642640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320546 (or 320540 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 29.

The square root of 25642640 is about 5063.8562380858. The cubic root of 25642640 is about 294.8860615242.

The spelling of 25642640 in words is "twenty-five million, six hundred forty-two thousand, six hundred forty".