2185505800865 has 4 divisors (see below), whose sum is σ = 2622606961044. Its totient is φ = 1748404640688.

The previous prime is 2185505800781. The next prime is 2185505800867. The reversal of 2185505800865 is 5680085055812.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1326845964544 + 858659836321 = 1151888^2 + 926639^2 .

It is a cyclic number.

It is not a de Polignac number, because 2185505800865 - 2⁸ = 2185505800609 is a prime.

It is a super-2 number, since 2×2185505800865² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (2185505800867) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 218550580082 + ... + 218550580091.

It is an arithmetic number, because the mean of its divisors is an integer number (655651740261).

Almost surely, 2^{2185505800865} is an apocalyptic number.

It is an amenable number.

2185505800865 is a deficient number, since it is larger than the sum of its proper divisors (437101160179).

2185505800865 is an equidigital number, since it uses as much as digits as its factorization.

2185505800865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 437101160178.

The product of its (nonzero) digits is 3840000, while the sum is 53.

The spelling of 2185505800865 in words is "two trillion, one hundred eighty-five billion, five hundred five million, eight hundred thousand, eight hundred sixty-five".