1664865445 has 4 divisors (see below), whose sum is σ = 1997838540. Its totient is φ = 1331892352.

The previous prime is 1664865427. The next prime is 1664865451. The reversal of 1664865445 is 5445684661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5445684661 = 401 ⋅13580261.

It can be written as a sum of positive squares in 2 ways, for example, as 225270081 + 1439595364 = 15009^2 + 37942^2 .

It is a cyclic number.

It is not a de Polignac number, because 1664865445 - 2⁵ = 1664865413 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent 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, 166486540 + ... + 166486549.

It is an arithmetic number, because the mean of its divisors is an integer number (499459635).

Almost surely, 2^1664865445 is an apocalyptic number.

It is an amenable number.

1664865445 is a deficient number, since it is larger than the sum of its proper divisors (332973095).

1664865445 is an equidigital number, since it uses as much as digits as its factorization.

1664865445 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 332973094.

The product of its digits is 2764800, while the sum is 49.

The square root of 1664865445 is about 40802.7627128360. The cubic root of 1664865445 is about 1185.2038306521.

The spelling of 1664865445 in words is "one billion, six hundred sixty-four million, eight hundred sixty-five thousand, four hundred forty-five".