664075661 has 2 divisors, whose sum is σ = 664075662. Its totient is φ = 664075660.

The previous prime is 664075609. The next prime is 664075663. The reversal of 664075661 is 166570466.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 624700036 + 39375625 = 24994^2 + 6275^2 .

It is a cyclic number.

It is not a de Polignac number, because 664075661 - 2⁶ = 664075597 is a prime.

It is a Sophie Germain prime.

Together with 664075663, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (664075663) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332037830 + 332037831.

It is an arithmetic number, because the mean of its divisors is an integer number (332037831).

Almost surely, 2^664075661 is an apocalyptic number.

It is an amenable number.

664075661 is a deficient number, since it is larger than the sum of its proper divisors (1).

664075661 is an equidigital number, since it uses as much as digits as its factorization.

664075661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 181440, while the sum is 41.

The square root of 664075661 is about 25769.6655197540. The cubic root of 664075661 is about 872.4472694410.

The spelling of 664075661 in words is "six hundred sixty-four million, seventy-five thousand, six hundred sixty-one".