2165543121 has 16 divisors (see below), whose sum is σ = 3332550528. Its totient is φ = 1225200000.

The previous prime is 2165543119. The next prime is 2165543197. The reversal of 2165543121 is 1213455612.

It is not a de Polignac number, because 2165543121 - 2¹ = 2165543119 is a prime.

It is not an unprimeable number, because it can be changed into a prime (2165543111) 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 15 ways as a sum of consecutive naturals, for example, 508380 + ... + 512621.

It is an arithmetic number, because the mean of its divisors is an integer number (208284408).

Almost surely, 2^2165543121 is an apocalyptic number.

2165543121 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

2165543121 is a deficient number, since it is larger than the sum of its proper divisors (1167007407).

2165543121 is a wasteful number, since it uses less digits than its factorization.

2165543121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1021112.

The product of its digits is 7200, while the sum is 30.

The square root of 2165543121 is about 46535.3964311039. The cubic root of 2165543121 is about 1293.7656372634.

Adding to 2165543121 its reverse (1213455612), we get a palindrome (3378998733).

The spelling of 2165543121 in words is "two billion, one hundred sixty-five million, five hundred forty-three thousand, one hundred twenty-one".