25728809 has 2 divisors, whose sum is σ = 25728810. Its totient is φ = 25728808.

The previous prime is 25728721. The next prime is 25728811. The reversal of 25728809 is 90882752.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17405584 + 8323225 = 4172^2 + 2885^2 .

It is a cyclic number.

It is not a de Polignac number, because 25728809 - 2⁸ = 25728553 is a prime.

It is a super-2 number, since 2×25728809² = 1323943225116962, which contains 22 as substring.

Together with 25728811, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (25728839) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12864404 + 12864405.

It is an arithmetic number, because the mean of its divisors is an integer number (12864405).

Almost surely, 2^25728809 is an apocalyptic number.

It is an amenable number.

25728809 is a deficient number, since it is larger than the sum of its proper divisors (1).

25728809 is an equidigital number, since it uses as much as digits as its factorization.

25728809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 80640, while the sum is 41.

The square root of 25728809 is about 5072.3573415129. The cubic root of 25728809 is about 295.2160019099.

The spelling of 25728809 in words is "twenty-five million, seven hundred twenty-eight thousand, eight hundred nine".