2161805 has 16 divisors (see below), whose sum is σ = 2844720. Its totient is φ = 1569792.

The previous prime is 2161787. The next prime is 2161813. The reversal of 2161805 is 5081612.

2161805 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 8 ways, for example, as 162409 + 1999396 = 403^2 + 1414^2 .

It is a cyclic number.

It is not a de Polignac number, because 2161805 - 2¹² = 2157709 is a prime.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

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 in 15 ways as a sum of consecutive naturals, for example, 2027 + ... + 2903.

It is an arithmetic number, because the mean of its divisors is an integer number (177795).

2^2161805 is an apocalyptic number.

It is an amenable number.

2161805 is a deficient number, since it is larger than the sum of its proper divisors (682915).

2161805 is a wasteful number, since it uses less digits than its factorization.

2161805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 928.

The product of its (nonzero) digits is 480, while the sum is 23.

The square root of 2161805 is about 1470.3077909064. The cubic root of 2161805 is about 129.3020783640.

It can be divided in two parts, 2 and 161805, that multiplied together give a triangular number (323610 = T₈₀₄).

The spelling of 2161805 in words is "two million, one hundred sixty-one thousand, eight hundred five".