686665261 has 2 divisors, whose sum is σ = 686665262. Its totient is φ = 686665260.

The previous prime is 686665223. The next prime is 686665279. The reversal of 686665261 is 162566686.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 673662025 + 13003236 = 25955^2 + 3606^2 .

It is a cyclic number.

It is not a de Polignac number, because 686665261 - 2⁹ = 686664749 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (686665061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343332630 + 343332631.

It is an arithmetic number, because the mean of its divisors is an integer number (343332631).

Almost surely, 2^686665261 is an apocalyptic number.

It is an amenable number.

686665261 is a deficient number, since it is larger than the sum of its proper divisors (1).

686665261 is an equidigital number, since it uses as much as digits as its factorization.

686665261 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 622080, while the sum is 46.

The square root of 686665261 is about 26204.2985214258. The cubic root of 686665261 is about 882.2297368100.

It can be divided in two parts, 6866 and 65261, that added together give a palindrome (72127).

The spelling of 686665261 in words is "six hundred eighty-six million, six hundred sixty-five thousand, two hundred sixty-one".