665515521 has 48 divisors (see below), whose sum is σ = 1092419328. Its totient is φ = 401533200.

The previous prime is 665515481. The next prime is 665515553. The reversal of 665515521 is 125515566.

665515521 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 665515521 - 2⁹ = 665515009 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (665515561) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 820206 + ... + 821016.

It is an arithmetic number, because the mean of its divisors is an integer number (22758736).

Almost surely, 2^665515521 is an apocalyptic number.

It is an amenable number.

665515521 is a deficient number, since it is larger than the sum of its proper divisors (426903807).

665515521 is a wasteful number, since it uses less digits than its factorization.

665515521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1144 (or 1132 counting only the distinct ones).

The product of its digits is 45000, while the sum is 36.

The square root of 665515521 is about 25797.5875034857. The cubic root of 665515521 is about 873.0773658718.

The spelling of 665515521 in words is "six hundred sixty-five million, five hundred fifteen thousand, five hundred twenty-one".