25805866661 has 2 divisors, whose sum is σ = 25805866662. Its totient is φ = 25805866660.

The previous prime is 25805866657. The next prime is 25805866693. The reversal of 25805866661 is 16666850852.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21475437025 + 4330429636 = 146545^2 + 65806^2 .

It is a cyclic number.

It is not a de Polignac number, because 25805866661 - 2² = 25805866657 is a prime.

It is a super-2 number, since 2×25805866661² (a number of 22 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (25805866631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12902933330 + 12902933331.

It is an arithmetic number, because the mean of its divisors is an integer number (12902933331).

Almost surely, 2^25805866661 is an apocalyptic number.

It is an amenable number.

25805866661 is a deficient number, since it is larger than the sum of its proper divisors (1).

25805866661 is an equidigital number, since it uses as much as digits as its factorization.

25805866661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4147200, while the sum is 53.

The spelling of 25805866661 in words is "twenty-five billion, eight hundred five million, eight hundred sixty-six thousand, six hundred sixty-one".