664561109 has 2 divisors, whose sum is σ = 664561110. Its totient is φ = 664561108.

The previous prime is 664561099. The next prime is 664561111. The reversal of 664561109 is 901165466.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 465610084 + 198951025 = 21578^2 + 14105^2 .

It is a cyclic number.

It is not a de Polignac number, because 664561109 - 2²⁴ = 647783893 is a prime.

Together with 664561111, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (664561199) by changing a digit.

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 as a sum of consecutive naturals, namely, 332280554 + 332280555.

It is an arithmetic number, because the mean of its divisors is an integer number (332280555).

Almost surely, 2^664561109 is an apocalyptic number.

It is an amenable number.

664561109 is a deficient number, since it is larger than the sum of its proper divisors (1).

664561109 is an equidigital number, since it uses as much as digits as its factorization.

664561109 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 38880, while the sum is 38.

The square root of 664561109 is about 25779.0827804249. The cubic root of 664561109 is about 872.6598077843.

The spelling of 664561109 in words is "six hundred sixty-four million, five hundred sixty-one thousand, one hundred nine".