664788728585 has 4 divisors (see below), whose sum is σ = 797746474308. Its totient is φ = 531830982864.

The previous prime is 664788728573. The next prime is 664788728587. The reversal of 664788728585 is 585827887466.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 245147775376 + 419640953209 = 495124^2 + 647797^2 .

It is a cyclic number.

It is not a de Polignac number, because 664788728585 - 2²⁰ = 664787680009 is a prime.

It is a super-2 number, since 2×664788728585² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (664788728587) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66478872854 + ... + 66478872863.

It is an arithmetic number, because the mean of its divisors is an integer number (199436618577).

Almost surely, 2^664788728585 is an apocalyptic number.

It is an amenable number.

664788728585 is a deficient number, since it is larger than the sum of its proper divisors (132957745723).

664788728585 is a wasteful number, since it uses less digits than its factorization.

664788728585 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 132957745722.

The product of its digits is 1445068800, while the sum is 74.

The spelling of 664788728585 in words is "six hundred sixty-four billion, seven hundred eighty-eight million, seven hundred twenty-eight thousand, five hundred eighty-five".