85781 has 2 divisors, whose sum is σ = 85782. Its totient is φ = 85780.

The previous prime is 85751. The next prime is 85793. The reversal of 85781 is 18758.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 84100 + 1681 = 290^2 + 41^2 .

It is a cyclic number.

It is not a de Polignac number, because 85781 - 2⁶ = 85717 is a prime.

It is a super-2 number, since 2×85781² = 14716759922, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (85711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 42890 + 42891.

It is an arithmetic number, because the mean of its divisors is an integer number (42891).

2⁸⁵⁷⁸¹ is an apocalyptic number.

It is an amenable number.

85781 is a deficient number, since it is larger than the sum of its proper divisors (1).

85781 is an equidigital number, since it uses as much as digits as its factorization.

85781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2240, while the sum is 29.

The square root of 85781 is about 292.8839360566. The cubic root of 85781 is about 44.1025500588.

The spelling of 85781 in words is "eighty-five thousand, seven hundred eighty-one".