664721461 has 2 divisors, whose sum is σ = 664721462. Its totient is φ = 664721460.

The previous prime is 664721419. The next prime is 664721467. The reversal of 664721461 is 164127466.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 582256900 + 82464561 = 24130^2 + 9081^2 .

It is a cyclic number.

It is not a de Polignac number, because 664721461 - 2⁹ = 664720949 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 664721461.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (664721467) 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, 332360730 + 332360731.

It is an arithmetic number, because the mean of its divisors is an integer number (332360731).

Almost surely, 2^664721461 is an apocalyptic number.

It is an amenable number.

664721461 is a deficient number, since it is larger than the sum of its proper divisors (1).

664721461 is an equidigital number, since it uses as much as digits as its factorization.

664721461 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 48384, while the sum is 37.

The square root of 664721461 is about 25782.1927112494. The cubic root of 664721461 is about 872.7299901901.

The spelling of 664721461 in words is "six hundred sixty-four million, seven hundred twenty-one thousand, four hundred sixty-one".