261685889 has 2 divisors, whose sum is σ = 261685890. Its totient is φ = 261685888.

The previous prime is 261685877. The next prime is 261685891. The reversal of 261685889 is 988586162.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 201157489 + 60528400 = 14183^2 + 7780^2 .

It is a cyclic number.

It is not a de Polignac number, because 261685889 - 2¹² = 261681793 is a prime.

Together with 261685891, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 261685889.

It is not a weakly prime, because it can be changed into another prime (261685819) 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, 130842944 + 130842945.

It is an arithmetic number, because the mean of its divisors is an integer number (130842945).

Almost surely, 2^261685889 is an apocalyptic number.

It is an amenable number.

261685889 is a deficient number, since it is larger than the sum of its proper divisors (1).

261685889 is an equidigital number, since it uses as much as digits as its factorization.

261685889 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1658880, while the sum is 53.

The square root of 261685889 is about 16176.7082250994. The cubic root of 261685889 is about 639.6269709331.

The spelling of 261685889 in words is "two hundred sixty-one million, six hundred eighty-five thousand, eight hundred eighty-nine".