664423101521 has 2 divisors, whose sum is σ = 664423101522. Its totient is φ = 664423101520.

The previous prime is 664423101497. The next prime is 664423101527. The reversal of 664423101521 is 125101324466.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 647962211521 + 16460890000 = 804961^2 + 128300^2 .

It is a cyclic number.

It is not a de Polignac number, because 664423101521 - 2³⁰ = 663349359697 is a prime.

It is not a weakly prime, because it can be changed into another prime (664423101527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332211550760 + 332211550761.

It is an arithmetic number, because the mean of its divisors is an integer number (332211550761).

Almost surely, 2^664423101521 is an apocalyptic number.

It is an amenable number.

664423101521 is a deficient number, since it is larger than the sum of its proper divisors (1).

664423101521 is an equidigital number, since it uses as much as digits as its factorization.

664423101521 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 35.

Adding to 664423101521 its reverse (125101324466), we get a palindrome (789524425987).

The spelling of 664423101521 in words is "six hundred sixty-four billion, four hundred twenty-three million, one hundred one thousand, five hundred twenty-one".