2159721809 has 4 divisors (see below), whose sum is σ = 2468253504. Its totient is φ = 1851190116.

The previous prime is 2159721791. The next prime is 2159721821. The reversal of 2159721809 is 9081279512.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 2159721809 - 2¹⁶ = 2159656273 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 2159721809.

It is not an unprimeable number, because it can be changed into a prime (2159721899) 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, 154265837 + ... + 154265850.

It is an arithmetic number, because the mean of its divisors is an integer number (617063376).

Almost surely, 2^2159721809 is an apocalyptic number.

It is an amenable number.

2159721809 is a deficient number, since it is larger than the sum of its proper divisors (308531695).

2159721809 is an equidigital number, since it uses as much as digits as its factorization.

2159721809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 308531694.

The product of its (nonzero) digits is 90720, while the sum is 44.

The square root of 2159721809 is about 46472.8071994796. The cubic root of 2159721809 is about 1292.6053167902.

The spelling of 2159721809 in words is "two billion, one hundred fifty-nine million, seven hundred twenty-one thousand, eight hundred nine".