2161221109 has 4 divisors (see below), whose sum is σ = 2161470220. Its totient is φ = 2160972000.

The previous prime is 2161221071. The next prime is 2161221113. The reversal of 2161221109 is 9011221612.

It is a happy number.

2161221109 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 1524668209 + 636552900 = 39047^2 + 25230^2 .

It is a cyclic number.

It is not a de Polignac number, because 2161221109 - 2¹⁷ = 2161090037 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 (2161231109) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 111054 + ... + 129055.

It is an arithmetic number, because the mean of its divisors is an integer number (540367555).

Almost surely, 2^2161221109 is an apocalyptic number.

It is an amenable number.

2161221109 is a deficient number, since it is larger than the sum of its proper divisors (249111).

2161221109 is an equidigital number, since it uses as much as digits as its factorization.

2161221109 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 249110.

The product of its (nonzero) digits is 432, while the sum is 25.

The square root of 2161221109 is about 46488.9353394977. The cubic root of 2161221109 is about 1292.9043606849.

The spelling of 2161221109 in words is "two billion, one hundred sixty-one million, two hundred twenty-one thousand, one hundred nine".