664724521 has 2 divisors, whose sum is σ = 664724522. Its totient is φ = 664724520.

The previous prime is 664724479. The next prime is 664724527. The reversal of 664724521 is 125427466.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 336208896 + 328515625 = 18336^2 + 18125^2 .

It is a cyclic number.

It is not a de Polignac number, because 664724521 - 2⁷ = 664724393 is a prime.

It is not a weakly prime, because it can be changed into another prime (664724527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332362260 + 332362261.

It is an arithmetic number, because the mean of its divisors is an integer number (332362261).

Almost surely, 2^664724521 is an apocalyptic number.

It is an amenable number.

664724521 is a deficient number, since it is larger than the sum of its proper divisors (1).

664724521 is an equidigital number, since it uses as much as digits as its factorization.

664724521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 80640, while the sum is 37.

The square root of 664724521 is about 25782.2520544657. The cubic root of 664724521 is about 872.7313293724.

The spelling of 664724521 in words is "six hundred sixty-four million, seven hundred twenty-four thousand, five hundred twenty-one".