2166623209 has 9 divisors (see below), whose sum is σ = 2195438583. Its totient is φ = 2138182992.

The previous prime is 2166623197. The next prime is 2166623227. The reversal of 2166623209 is 9023266612.

The square root of 2166623209 is 46547.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 416037609 + 1750585600 = 20397^2 + 41840^2 .

It is not a de Polignac number, because 2166623209 - 2⁹ = 2166622697 is a prime.

It is a super-2 number, since 2×2166623209² = 9388512259554915362, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2166623609) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 4142422 + ... + 4142944.

Almost surely, 2^2166623209 is an apocalyptic number.

2166623209 is the 46547-th square number.

2166623209 is the 23274-th centered octagonal number.

It is an amenable number.

2166623209 is a deficient number, since it is larger than the sum of its proper divisors (28815374).

2166623209 is an frugal number, since it uses more digits than its factorization.

2166623209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1224 (or 612 counting only the distinct ones).

The product of its (nonzero) digits is 46656, while the sum is 37.

The cubic root of 2166623209 is about 1293.9806947042.

Multiplying 2166623209 by its product of nonzero digits (46656), we get a square (101085972439104 = 10054152²).

The spelling of 2166623209 in words is "two billion, one hundred sixty-six million, six hundred twenty-three thousand, two hundred nine".