25640809 has 2 divisors, whose sum is σ = 25640810. Its totient is φ = 25640808.

The previous prime is 25640807. The next prime is 25640831. The reversal of 25640809 is 90804652.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 23474025 + 2166784 = 4845^2 + 1472^2 .

It is a cyclic number.

It is not a de Polignac number, because 25640809 - 2¹ = 25640807 is a prime.

Together with 25640807, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (25640807) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12820404 + 12820405.

It is an arithmetic number, because the mean of its divisors is an integer number (12820405).

Almost surely, 2^25640809 is an apocalyptic number.

It is an amenable number.

25640809 is a deficient number, since it is larger than the sum of its proper divisors (1).

25640809 is an equidigital number, since it uses as much as digits as its factorization.

25640809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 17280, while the sum is 34.

The square root of 25640809 is about 5063.6754437859. The cubic root of 25640809 is about 294.8790426261.

The spelling of 25640809 in words is "twenty-five million, six hundred forty thousand, eight hundred nine".