1664394689 has 2 divisors, whose sum is σ = 1664394690. Its totient is φ = 1664394688.

The previous prime is 1664394629. The next prime is 1664394703. The reversal of 1664394689 is 9864934661.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1351812289 + 312582400 = 36767^2 + 17680^2 .

It is an emirp because it is prime and its reverse (9864934661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1664394689 - 2²⁴ = 1647617473 is a prime.

It is not a weakly prime, because it can be changed into another prime (1664394629) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832197344 + 832197345.

It is an arithmetic number, because the mean of its divisors is an integer number (832197345).

Almost surely, 2^1664394689 is an apocalyptic number.

It is an amenable number.

1664394689 is a deficient number, since it is larger than the sum of its proper divisors (1).

1664394689 is an equidigital number, since it uses as much as digits as its factorization.

1664394689 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6718464, while the sum is 56.

The square root of 1664394689 is about 40796.9936269819. The cubic root of 1664394689 is about 1185.0921110309.

The spelling of 1664394689 in words is "one billion, six hundred sixty-four million, three hundred ninety-four thousand, six hundred eighty-nine".