1664378645 has 4 divisors (see below), whose sum is σ = 1997254380. Its totient is φ = 1331502912.

The previous prime is 1664378581. The next prime is 1664378657. The reversal of 1664378645 is 5468734661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5468734661 = 13 ⋅420671897.

It can be written as a sum of positive squares in 2 ways, for example, as 480881041 + 1183497604 = 21929^2 + 34402^2 .

It is a cyclic number.

It is not a de Polignac number, because 1664378645 - 2⁶ = 1664378581 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1664378593 and 1664378602.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 166437860 + ... + 166437869.

It is an arithmetic number, because the mean of its divisors is an integer number (499313595).

Almost surely, 2^1664378645 is an apocalyptic number.

It is an amenable number.

1664378645 is a deficient number, since it is larger than the sum of its proper divisors (332875735).

1664378645 is an equidigital number, since it uses as much as digits as its factorization.

1664378645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 332875734.

The product of its digits is 2903040, while the sum is 50.

The square root of 1664378645 is about 40796.7969943720. The cubic root of 1664378645 is about 1185.0883031042.

The spelling of 1664378645 in words is "one billion, six hundred sixty-four million, three hundred seventy-eight thousand, six hundred forty-five".