2221661665 has 4 divisors (see below), whose sum is σ = 2665994004. Its totient is φ = 1777329328.

The previous prime is 2221661623. The next prime is 2221661723. The reversal of 2221661665 is 5661661222.

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 1388531169 + 833130496 = 37263^2 + 28864^2 .

It is a cyclic number.

It is not a de Polignac number, because 2221661665 - 2⁷ = 2221661537 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 222166162 + ... + 222166171.

It is an arithmetic number, because the mean of its divisors is an integer number (666498501).

Almost surely, 2^2221661665 is an apocalyptic number.

It is an amenable number.

2221661665 is a deficient number, since it is larger than the sum of its proper divisors (444332339).

2221661665 is an equidigital number, since it uses as much as digits as its factorization.

2221661665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 444332338.

The product of its digits is 51840, while the sum is 37.

The square root of 2221661665 is about 47134.5060969138. The cubic root of 2221661665 is about 1304.8461457957.

The spelling of 2221661665 in words is "two billion, two hundred twenty-one million, six hundred sixty-one thousand, six hundred sixty-five".