865261 has 2 divisors, whose sum is σ = 865262. Its totient is φ = 865260.

The previous prime is 865259. The next prime is 865301. The reversal of 865261 is 162568.

865261 = T₇₅₈ + T₇₅₉ + T₇₆₀.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 864900 + 361 = 930^2 + 19^2 .

It is a cyclic number.

It is not a de Polignac number, because 865261 - 2¹ = 865259 is a prime.

Together with 865259, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (865201) 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, 432630 + 432631.

It is an arithmetic number, because the mean of its divisors is an integer number (432631).

2⁸⁶⁵²⁶¹ is an apocalyptic number.

865261 is the 760-th centered triangular number.

It is an amenable number.

865261 is a deficient number, since it is larger than the sum of its proper divisors (1).

865261 is an equidigital number, since it uses as much as digits as its factorization.

865261 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2880, while the sum is 28.

The square root of 865261 is about 930.1940657734. The cubic root of 865261 is about 95.2903765368.

The spelling of 865261 in words is "eight hundred sixty-five thousand, two hundred sixty-one".