2161999 has 4 divisors (see below), whose sum is σ = 2470864. Its totient is φ = 1853136.

The previous prime is 2161987. The next prime is 2162003. The reversal of 2161999 is 9991612.

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

It is a cyclic number.

It is not a de Polignac number, because 2161999 - 2⁵ = 2161967 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2161919) 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 in 3 ways as a sum of consecutive naturals, for example, 154422 + ... + 154435.

It is an arithmetic number, because the mean of its divisors is an integer number (617716).

2^2161999 is an apocalyptic number.

2161999 is a deficient number, since it is larger than the sum of its proper divisors (308865).

2161999 is an equidigital number, since it uses as much as digits as its factorization.

2161999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 308864.

The product of its digits is 8748, while the sum is 37.

The square root of 2161999 is about 1470.3737620075. The cubic root of 2161999 is about 129.3059460969.

It can be divided in two parts, 2161 and 999, that added together give a triangular number (3160 = T₇₉).

The spelling of 2161999 in words is "two million, one hundred sixty-one thousand, nine hundred ninety-nine".