2165721187 has 8 divisors (see below), whose sum is σ = 2532670976. Its totient is φ = 1813161672.

The previous prime is 2165721169. The next prime is 2165721197. The reversal of 2165721187 is 7811275612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 2165721187 - 2⁷ = 2165721059 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2165721127) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 3597243 + ... + 3597844.

It is an arithmetic number, because the mean of its divisors is an integer number (316583872).

Almost surely, 2^2165721187 is an apocalyptic number.

2165721187 is a deficient number, since it is larger than the sum of its proper divisors (366949789).

2165721187 is an equidigital number, since it uses as much as digits as its factorization.

2165721187 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7195137.

The product of its digits is 47040, while the sum is 40.

The square root of 2165721187 is about 46537.3096235698. The cubic root of 2165721187 is about 1293.8010970912.

Adding to 2165721187 its reverse (7811275612), we get a palindrome (9976996799).

The spelling of 2165721187 in words is "two billion, one hundred sixty-five million, seven hundred twenty-one thousand, one hundred eighty-seven".