664240561 has 2 divisors, whose sum is σ = 664240562. Its totient is φ = 664240560.

The previous prime is 664240559. The next prime is 664240601. The reversal of 664240561 is 165042466.

664240561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 569061025 + 95179536 = 23855^2 + 9756^2 .

It is a cyclic number.

It is not a de Polignac number, because 664240561 - 2¹ = 664240559 is a prime.

It is a super-6 number, since 6×664240561⁶ (a number of 54 digits) contains 666666 as substring.

Together with 664240559, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (664240531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332120280 + 332120281.

It is an arithmetic number, because the mean of its divisors is an integer number (332120281).

Almost surely, 2^664240561 is an apocalyptic number.

It is an amenable number.

664240561 is a deficient number, since it is larger than the sum of its proper divisors (1).

664240561 is an equidigital number, since it uses as much as digits as its factorization.

664240561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 34560, while the sum is 34.

The square root of 664240561 is about 25772.8648194181. The cubic root of 664240561 is about 872.5194774020.

It can be divided in two parts, 6642405 and 61, that added together give a palindrome (6642466).

The spelling of 664240561 in words is "six hundred sixty-four million, two hundred forty thousand, five hundred sixty-one".