25815561 has 4 divisors (see below), whose sum is σ = 34420752. Its totient is φ = 17210372.

The previous prime is 25815553. The next prime is 25815563. The reversal of 25815561 is 16551852.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 25815561 - 2³ = 25815553 is a prime.

It is not an unprimeable number, because it can be changed into a prime (25815563) 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 in 3 ways as a sum of consecutive naturals, for example, 4302591 + ... + 4302596.

It is an arithmetic number, because the mean of its divisors is an integer number (8605188).

Almost surely, 2^25815561 is an apocalyptic number.

It is an amenable number.

25815561 is a deficient number, since it is larger than the sum of its proper divisors (8605191).

25815561 is an equidigital number, since it uses as much as digits as its factorization.

25815561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8605190.

The product of its digits is 12000, while the sum is 33.

The square root of 25815561 is about 5080.9015932214. The cubic root of 25815561 is about 295.5474312679.

The spelling of 25815561 in words is "twenty-five million, eight hundred fifteen thousand, five hundred sixty-one".