665164521 has 48 divisors (see below), whose sum is σ = 1188720000. Its totient is φ = 360052128.

The previous prime is 665164501. The next prime is 665164523. The reversal of 665164521 is 125461566.

665164521 is a `hidden beast` number, since 6 + 6 + 5 + 1 + 645 + 2 + 1 = 666.

It is not a de Polignac number, because 665164521 - 2¹⁹ = 664640233 is a prime.

It is a super-3 number, since 3×665164521³ (a number of 27 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (665164523) 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 in 47 ways as a sum of consecutive naturals, for example, 63355 + ... + 73103.

It is an arithmetic number, because the mean of its divisors is an integer number (24765000).

Almost surely, 2^665164521 is an apocalyptic number.

It is an amenable number.

665164521 is a deficient number, since it is larger than the sum of its proper divisors (523555479).

665164521 is a wasteful number, since it uses less digits than its factorization.

665164521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9803 (or 9778 counting only the distinct ones).

The product of its digits is 43200, while the sum is 36.

The square root of 665164521 is about 25790.7836445502. The cubic root of 665164521 is about 872.9238487679.

The spelling of 665164521 in words is "six hundred sixty-five million, one hundred sixty-four thousand, five hundred twenty-one".