25806661 has 4 divisors (see below), whose sum is σ = 25818732. Its totient is φ = 25794592.

The previous prime is 25806647. The next prime is 25806679. The reversal of 25806661 is 16660852.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 2910436 + 22896225 = 1706^2 + 4785^2 .

It is a cyclic number.

It is not a de Polignac number, because 25806661 - 2⁷ = 25806533 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (25806461) 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, 1870 + ... + 7423.

It is an arithmetic number, because the mean of its divisors is an integer number (6454683).

Almost surely, 2^25806661 is an apocalyptic number.

It is an amenable number.

25806661 is a deficient number, since it is larger than the sum of its proper divisors (12071).

25806661 is an equidigital number, since it uses as much as digits as its factorization.

25806661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12070.

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

The square root of 25806661 is about 5080.0256889114. The cubic root of 25806661 is about 295.5134637128.

The spelling of 25806661 in words is "twenty-five million, eight hundred six thousand, six hundred sixty-one".