85661809 has 2 divisors, whose sum is σ = 85661810. Its totient is φ = 85661808.

The previous prime is 85661803. The next prime is 85661813. The reversal of 85661809 is 90816658.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 71031184 + 14630625 = 8428^2 + 3825^2 .

It is a cyclic number.

It is not a de Polignac number, because 85661809 - 2¹⁵ = 85629041 is a prime.

It is not a weakly prime, because it can be changed into another prime (85661803) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 42830904 + 42830905.

It is an arithmetic number, because the mean of its divisors is an integer number (42830905).

Almost surely, 2^85661809 is an apocalyptic number.

It is an amenable number.

85661809 is a deficient number, since it is larger than the sum of its proper divisors (1).

85661809 is an equidigital number, since it uses as much as digits as its factorization.

85661809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 103680, while the sum is 43.

The square root of 85661809 is about 9255.3664973355. The cubic root of 85661809 is about 440.8211405090.

The spelling of 85661809 in words is "eighty-five million, six hundred sixty-one thousand, eight hundred nine".