2209816561 has 4 divisors (see below), whose sum is σ = 2246043124. Its totient is φ = 2173590000.

The previous prime is 2209816549. The next prime is 2209816577. The reversal of 2209816561 is 1656189022.

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 113550336 + 2096266225 = 10656^2 + 45785^2 .

It is a cyclic number.

It is not a de Polignac number, because 2209816561 - 2³¹ = 62332913 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2209811561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18113190 + ... + 18113311.

It is an arithmetic number, because the mean of its divisors is an integer number (561510781).

Almost surely, 2^2209816561 is an apocalyptic number.

It is an amenable number.

2209816561 is a deficient number, since it is larger than the sum of its proper divisors (36226563).

2209816561 is an equidigital number, since it uses as much as digits as its factorization.

2209816561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36226562.

The product of its (nonzero) digits is 51840, while the sum is 40.

The square root of 2209816561 is about 47008.6860165225. The cubic root of 2209816561 is about 1302.5230214898.

The spelling of 2209816561 in words is "two billion, two hundred nine million, eight hundred sixteen thousand, five hundred sixty-one".