2166405778 has 16 divisors (see below), whose sum is σ = 3499083360. Its totient is φ = 1002204736.

The previous prime is 2166405737. The next prime is 2166405799. The reversal of 2166405778 is 8775046612.

It is a happy number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 537976 + ... + 541987.

It is an arithmetic number, because the mean of its divisors is an integer number (218692710).

Almost surely, 2^2166405778 is an apocalyptic number.

2166405778 is a deficient number, since it is larger than the sum of its proper divisors (1332677582).

2166405778 is a wasteful number, since it uses less digits than its factorization.

2166405778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1080041.

The product of its (nonzero) digits is 564480, while the sum is 46.

The square root of 2166405778 is about 46544.6643343789. The cubic root of 2166405778 is about 1293.9374075393.

The spelling of 2166405778 in words is "two billion, one hundred sixty-six million, four hundred five thousand, seven hundred seventy-eight".